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"text": "# DBI (perldoc)\n\n## NAME\n\nDBI - Database independent interface for Perl\n\n## SYNOPSIS\n\nuse DBI;\n@drivernames = DBI->availabledrivers;\n%drivers = DBI->installeddrivers;\n@datasources = DBI->datasources($drivername, \\%attr);\n$dbh = DBI->connect($datasource, $username, $auth, \\%attr);\n$rv = $dbh->do($statement);\n$rv = $dbh->do($statement, \\%attr);\n$rv = $dbh->do($statement, \\%attr, @bindvalues);\n$aryref = $dbh->selectallarrayref($statement);\n$hashref = $dbh->selectallhashref($statement, $keyfield);\n$aryref = $dbh->selectcolarrayref($statement);\n$aryref = $dbh->selectcolarrayref($statement, \\%attr);\n@rowary = $dbh->selectrowarray($statement);\n$aryref = $dbh->selectrowarrayref($statement);\n$hashref = $dbh->selectrowhashref($statement);\n$sth = $dbh->prepare($statement);\n$sth = $dbh->preparecached($statement);\n$rc = $sth->bindparam($pnum, $bindvalue);\n$rc = $sth->bindparam($pnum, $bindvalue, $bindtype);\n$rc = $sth->bindparam($pnum, $bindvalue, \\%attr);\n$rv = $sth->execute;\n$rv = $sth->execute(@bindvalues);\n$rv = $sth->executearray(\\%attr, ...);\n$rc = $sth->bindcol($colnum, \\$colvariable);\n$rc = $sth->bindcolumns(@listofrefstovarstobind);\n@rowary = $sth->fetchrowarray;\n$aryref = $sth->fetchrowarrayref;\n$hashref = $sth->fetchrowhashref;\n$aryref = $sth->fetchallarrayref;\n$aryref = $sth->fetchallarrayref( $slice, $maxrows );\n$hashref = $sth->fetchallhashref( $keyfield );\n$rv = $sth->rows;\n$rc = $dbh->beginwork;\n$rc = $dbh->commit;\n$rc = $dbh->rollback;\n$quotedstring = $dbh->quote($string);\n$rc = $h->err;\n$str = $h->errstr;\n$rv = $h->state;\n$rc = $dbh->disconnect;\n*The synopsis above only lists the major methods and parameters.*\nGETTING HELP\nGeneral\nBefore asking any questions, reread this document, consult the archives and read the DBI FAQ.\nThe archives are listed at the end of this document and on the DBI home page\n\nYou might also like to read the Advanced DBI Tutorial at\n\nTo help you make the best use of the dbi-users mailing list, and any other lists or forums you\nmay use, I recommend that you read \"Getting Answers\" by Mike Ash:\n.\nMailing Lists\nIf you have questions about DBI, or DBD driver modules, you can get help from the\n*dbi-users@perl.org* mailing list. This is the best way to get help. You don't have to subscribe\nto the list in order to post, though I'd recommend it. You can get help on subscribing and using\nthe list by emailing *dbi-users-help@perl.org*.\nPlease note that Tim Bunce does not maintain the mailing lists or the web pages (generous\nvolunteers do that). So please don't send mail directly to him; he just doesn't have the time to\nanswer questions personally. The *dbi-users* mailing list has lots of experienced people who\nshould be able to help you if you need it. If you do email Tim he is very likely to just forward\nit to the mailing list.\nIRC\nDBI IRC Channel: #dbi on irc.perl.org ()\nOnline\nStackOverflow has a DBI tag with over 800\nquestions.\nThe DBI home page at and the DBI FAQ at may\nbe worth a visit. They include links to other resources, but *are rather out-dated*.\nReporting a Bug\nIf you think you've found a bug then please read \"How to Report Bugs Effectively\" by Simon\nTatham: .\nIf you think you've found a memory leak then read \"Memory Leaks\".\nYour problem is most likely related to the specific DBD driver module you're using. If that's\nthe case then click on the 'Bugs' link on the page for your driver. Only\nsubmit a bug report against the DBI itself if you're sure that your issue isn't related to the\ndriver you're using.\nNOTES\nThis is the DBI specification that corresponds to DBI version 1.642 (see DBI::Changes for\ndetails).\nThe DBI is evolving at a steady pace, so it's good to check that you have the latest copy.\nThe significant user-visible changes in each release are documented in the DBI::Changes module\nso you can read them by executing \"perldoc DBI::Changes\".\nSome DBI changes require changes in the drivers, but the drivers can take some time to catch up.\nNewer versions of the DBI have added features that may not yet be supported by the drivers you\nuse. Talk to the authors of your drivers if you need a new feature that is not yet supported.\nFeatures added after DBI 1.21 (February 2002) are marked in the text with the version number of\nthe DBI release they first appeared in.\nExtensions to the DBI API often use the \"DBIx::*\" namespace. See \"Naming Conventions and Name\nSpace\". DBI extension modules can be found at . And all\nmodules related to the DBI can be found at .\n\n## DESCRIPTION\n\nThe DBI is a database access module for the Perl programming language. It defines a set of\nmethods, variables, and conventions that provide a consistent database interface, independent of\nthe actual database being used.\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION** (5 subsections)\n- **THE DBI PACKAGE AND CLASS** (3 subsections)\n- **METHODS COMMON TO ALL HANDLES** (1 subsections)\n- **ATTRIBUTES COMMON TO ALL HANDLES** (3 subsections)\n- **DBI DATABASE HANDLE OBJECTS** (6 subsections)\n- **DBI STATEMENT HANDLE OBJECTS** (7 subsections)\n- **FURTHER INFORMATION** (10 subsections)\n- **TRACING** (8 subsections)\n- **DBI ENVIRONMENT VARIABLES**\n- **WARNING AND ERROR MESSAGES** (1 subsections)\n- **Pure-Perl DBI**\n- **SEE ALSO** (6 subsections)\n- **AUTHORS**\n- **COPYRIGHT**\n- **SUPPORT / WARRANTY** (2 subsections)\n- **ACKNOWLEDGEMENTS**\n- **CONTRIBUTING** (4 subsections)\n- **TRANSLATIONS**\n- **OTHER RELATED WORK AND PERL MODULES**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n"
}
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"command": "DBI",
"section": "",
"mode": "perldoc",
"summary": "DBI - Database independent interface for Perl",
"synopsis": "use DBI;\n@drivernames = DBI->availabledrivers;\n%drivers = DBI->installeddrivers;\n@datasources = DBI->datasources($drivername, \\%attr);\n$dbh = DBI->connect($datasource, $username, $auth, \\%attr);\n$rv = $dbh->do($statement);\n$rv = $dbh->do($statement, \\%attr);\n$rv = $dbh->do($statement, \\%attr, @bindvalues);\n$aryref = $dbh->selectallarrayref($statement);\n$hashref = $dbh->selectallhashref($statement, $keyfield);\n$aryref = $dbh->selectcolarrayref($statement);\n$aryref = $dbh->selectcolarrayref($statement, \\%attr);\n@rowary = $dbh->selectrowarray($statement);\n$aryref = $dbh->selectrowarrayref($statement);\n$hashref = $dbh->selectrowhashref($statement);\n$sth = $dbh->prepare($statement);\n$sth = $dbh->preparecached($statement);\n$rc = $sth->bindparam($pnum, $bindvalue);\n$rc = $sth->bindparam($pnum, $bindvalue, $bindtype);\n$rc = $sth->bindparam($pnum, $bindvalue, \\%attr);\n$rv = $sth->execute;\n$rv = $sth->execute(@bindvalues);\n$rv = $sth->executearray(\\%attr, ...);\n$rc = $sth->bindcol($colnum, \\$colvariable);\n$rc = $sth->bindcolumns(@listofrefstovarstobind);\n@rowary = $sth->fetchrowarray;\n$aryref = $sth->fetchrowarrayref;\n$hashref = $sth->fetchrowhashref;\n$aryref = $sth->fetchallarrayref;\n$aryref = $sth->fetchallarrayref( $slice, $maxrows );\n$hashref = $sth->fetchallhashref( $keyfield );\n$rv = $sth->rows;\n$rc = $dbh->beginwork;\n$rc = $dbh->commit;\n$rc = $dbh->rollback;\n$quotedstring = $dbh->quote($string);\n$rc = $h->err;\n$str = $h->errstr;\n$rv = $h->state;\n$rc = $dbh->disconnect;\n*The synopsis above only lists the major methods and parameters.*\nGETTING HELP\nGeneral\nBefore asking any questions, reread this document, consult the archives and read the DBI FAQ.\nThe archives are listed at the end of this document and on the DBI home page\n\nYou might also like to read the Advanced DBI Tutorial at\n\nTo help you make the best use of the dbi-users mailing list, and any other lists or forums you\nmay use, I recommend that you read \"Getting Answers\" by Mike Ash:\n.\nMailing Lists\nIf you have questions about DBI, or DBD driver modules, you can get help from the\n*dbi-users@perl.org* mailing list. This is the best way to get help. You don't have to subscribe\nto the list in order to post, though I'd recommend it. You can get help on subscribing and using\nthe list by emailing *dbi-users-help@perl.org*.\nPlease note that Tim Bunce does not maintain the mailing lists or the web pages (generous\nvolunteers do that). So please don't send mail directly to him; he just doesn't have the time to\nanswer questions personally. The *dbi-users* mailing list has lots of experienced people who\nshould be able to help you if you need it. If you do email Tim he is very likely to just forward\nit to the mailing list.\nIRC\nDBI IRC Channel: #dbi on irc.perl.org ()\nOnline\nStackOverflow has a DBI tag with over 800\nquestions.\nThe DBI home page at and the DBI FAQ at may\nbe worth a visit. They include links to other resources, but *are rather out-dated*.\nReporting a Bug\nIf you think you've found a bug then please read \"How to Report Bugs Effectively\" by Simon\nTatham: .\nIf you think you've found a memory leak then read \"Memory Leaks\".\nYour problem is most likely related to the specific DBD driver module you're using. If that's\nthe case then click on the 'Bugs' link on the page for your driver. Only\nsubmit a bug report against the DBI itself if you're sure that your issue isn't related to the\ndriver you're using.\nNOTES\nThis is the DBI specification that corresponds to DBI version 1.642 (see DBI::Changes for\ndetails).\nThe DBI is evolving at a steady pace, so it's good to check that you have the latest copy.\nThe significant user-visible changes in each release are documented in the DBI::Changes module\nso you can read them by executing \"perldoc DBI::Changes\".\nSome DBI changes require changes in the drivers, but the drivers can take some time to catch up.\nNewer versions of the DBI have added features that may not yet be supported by the drivers you\nuse. Talk to the authors of your drivers if you need a new feature that is not yet supported.\nFeatures added after DBI 1.21 (February 2002) are marked in the text with the version number of\nthe DBI release they first appeared in.\nExtensions to the DBI API often use the \"DBIx::*\" namespace. See \"Naming Conventions and Name\nSpace\". DBI extension modules can be found at . And all\nmodules related to the DBI can be found at .",
"tldr_summary": null,
"tldr_examples": [],
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"flags": [],
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"section_outline": [
{
"name": "NAME",
"lines": 2,
"subsections": []
},
{
"name": "SYNOPSIS",
"lines": 127,
"subsections": []
},
{
"name": "DESCRIPTION",
"lines": 13,
"subsections": [
{
"name": "Architecture of a DBI Application",
"lines": 23
},
{
"name": "Notation and Conventions",
"lines": 17
},
{
"name": "Outline Usage",
"lines": 121
},
{
"name": "Naming Conventions and Name Space",
"lines": 37
},
{
"name": "Placeholders and Bind Values",
"lines": 186
}
]
},
{
"name": "THE DBI PACKAGE AND CLASS",
"lines": 204,
"subsections": [
{
"name": "connect_cached",
"lines": 14
},
{
"name": "connect_cached",
"lines": 63
},
{
"name": "data_sources",
"lines": 241
}
]
},
{
"name": "METHODS COMMON TO ALL HANDLES",
"lines": 14,
"subsections": [
{
"name": "state",
"lines": 254
}
]
},
{
"name": "ATTRIBUTES COMMON TO ALL HANDLES",
"lines": 41,
"subsections": [
{
"name": "execute",
"lines": 279
},
{
"name": "set_err",
"lines": 31
},
{
"name": "set_err",
"lines": 401
}
]
},
{
"name": "DBI DATABASE HANDLE OBJECTS",
"lines": 2,
"subsections": [
{
"name": "Database Handle Methods",
"lines": 230
},
{
"name": "fetchall_hashref",
"lines": 467
},
{
"name": "table_info",
"lines": 47
},
{
"name": "table_info",
"lines": 435
},
{
"name": "take_imp_data",
"lines": 20
},
{
"name": "Database Handle Attributes",
"lines": 118
}
]
},
{
"name": "DBI STATEMENT HANDLE OBJECTS",
"lines": 2,
"subsections": [
{
"name": "Statement Handle Methods",
"lines": 48
},
{
"name": "bind_param",
"lines": 152
},
{
"name": "execute",
"lines": 96
},
{
"name": "execute_for_fetch",
"lines": 117
},
{
"name": "max",
"lines": 316
},
{
"name": "Statement Handle Attributes",
"lines": 195
},
{
"name": "bind_param",
"lines": 70
}
]
},
{
"name": "FURTHER INFORMATION",
"lines": 1,
"subsections": [
{
"name": "Catalog Methods",
"lines": 42
},
{
"name": "Transactions",
"lines": 65
},
{
"name": "Simple Examples",
"lines": 59
},
{
"name": "Threads and Thread Safety",
"lines": 29
},
{
"name": "Signal Handling and Canceling Operations",
"lines": 11
},
{
"name": "sigaction",
"lines": 116
},
{
"name": "Subclassing the DBI",
"lines": 46
},
{
"name": "connect",
"lines": 53
},
{
"name": "set_err",
"lines": 7
},
{
"name": "Memory Leaks",
"lines": 14
}
]
},
{
"name": "TRACING",
"lines": 3,
"subsections": [
{
"name": "Trace Settings",
"lines": 11
},
{
"name": "Trace Levels",
"lines": 19
},
{
"name": "Trace Flags",
"lines": 20
},
{
"name": "Enabling Trace",
"lines": 15
},
{
"name": "Trace Output",
"lines": 16
},
{
"name": "Tracing to Layered Filehandles",
"lines": 107
},
{
"name": "Trace Content",
"lines": 4
},
{
"name": "Tracing Tips",
"lines": 15
}
]
},
{
"name": "DBI ENVIRONMENT VARIABLES",
"lines": 66,
"subsections": []
},
{
"name": "WARNING AND ERROR MESSAGES",
"lines": 1,
"subsections": [
{
"name": "Fatal Errors",
"lines": 25
}
]
},
{
"name": "Pure-Perl DBI",
"lines": 3,
"subsections": []
},
{
"name": "SEE ALSO",
"lines": 1,
"subsections": [
{
"name": "Driver and Database Documentation",
"lines": 30
},
{
"name": "Standards Reference Information",
"lines": 11
},
{
"name": "Books and Articles",
"lines": 9
},
{
"name": "Perl Modules",
"lines": 16
},
{
"name": "Mailing List",
"lines": 14
},
{
"name": "Assorted Related Links",
"lines": 21
}
]
},
{
"name": "AUTHORS",
"lines": 5,
"subsections": []
},
{
"name": "COPYRIGHT",
"lines": 5,
"subsections": []
},
{
"name": "SUPPORT / WARRANTY",
"lines": 2,
"subsections": [
{
"name": "Support",
"lines": 4
},
{
"name": "Sponsor Enhancements",
"lines": 7
}
]
},
{
"name": "ACKNOWLEDGEMENTS",
"lines": 27,
"subsections": []
},
{
"name": "CONTRIBUTING",
"lines": 9,
"subsections": [
{
"name": "Browsing the source code repository",
"lines": 2
},
{
"name": "How to create a patch using Git",
"lines": 33
},
{
"name": "How to create a patch without Git",
"lines": 27
},
{
"name": "Speak before you patch",
"lines": 8
}
]
},
{
"name": "TRANSLATIONS",
"lines": 5,
"subsections": []
},
{
"name": "OTHER RELATED WORK AND PERL MODULES",
"lines": 9,
"subsections": []
}
],
"sections": {
"NAME": {
"content": "DBI - Database independent interface for Perl\n",
"subsections": []
},
"SYNOPSIS": {
"content": "use DBI;\n\n@drivernames = DBI->availabledrivers;\n%drivers = DBI->installeddrivers;\n@datasources = DBI->datasources($drivername, \\%attr);\n\n$dbh = DBI->connect($datasource, $username, $auth, \\%attr);\n\n$rv = $dbh->do($statement);\n$rv = $dbh->do($statement, \\%attr);\n$rv = $dbh->do($statement, \\%attr, @bindvalues);\n\n$aryref = $dbh->selectallarrayref($statement);\n$hashref = $dbh->selectallhashref($statement, $keyfield);\n\n$aryref = $dbh->selectcolarrayref($statement);\n$aryref = $dbh->selectcolarrayref($statement, \\%attr);\n\n@rowary = $dbh->selectrowarray($statement);\n$aryref = $dbh->selectrowarrayref($statement);\n$hashref = $dbh->selectrowhashref($statement);\n\n$sth = $dbh->prepare($statement);\n$sth = $dbh->preparecached($statement);\n\n$rc = $sth->bindparam($pnum, $bindvalue);\n$rc = $sth->bindparam($pnum, $bindvalue, $bindtype);\n$rc = $sth->bindparam($pnum, $bindvalue, \\%attr);\n\n$rv = $sth->execute;\n$rv = $sth->execute(@bindvalues);\n$rv = $sth->executearray(\\%attr, ...);\n\n$rc = $sth->bindcol($colnum, \\$colvariable);\n$rc = $sth->bindcolumns(@listofrefstovarstobind);\n\n@rowary = $sth->fetchrowarray;\n$aryref = $sth->fetchrowarrayref;\n$hashref = $sth->fetchrowhashref;\n\n$aryref = $sth->fetchallarrayref;\n$aryref = $sth->fetchallarrayref( $slice, $maxrows );\n\n$hashref = $sth->fetchallhashref( $keyfield );\n\n$rv = $sth->rows;\n\n$rc = $dbh->beginwork;\n$rc = $dbh->commit;\n$rc = $dbh->rollback;\n\n$quotedstring = $dbh->quote($string);\n\n$rc = $h->err;\n$str = $h->errstr;\n$rv = $h->state;\n\n$rc = $dbh->disconnect;\n\n*The synopsis above only lists the major methods and parameters.*\n\nGETTING HELP\nGeneral\nBefore asking any questions, reread this document, consult the archives and read the DBI FAQ.\nThe archives are listed at the end of this document and on the DBI home page\n\n\nYou might also like to read the Advanced DBI Tutorial at\n\n\nTo help you make the best use of the dbi-users mailing list, and any other lists or forums you\nmay use, I recommend that you read \"Getting Answers\" by Mike Ash:\n.\n\nMailing Lists\nIf you have questions about DBI, or DBD driver modules, you can get help from the\n*dbi-users@perl.org* mailing list. This is the best way to get help. You don't have to subscribe\nto the list in order to post, though I'd recommend it. You can get help on subscribing and using\nthe list by emailing *dbi-users-help@perl.org*.\n\nPlease note that Tim Bunce does not maintain the mailing lists or the web pages (generous\nvolunteers do that). So please don't send mail directly to him; he just doesn't have the time to\nanswer questions personally. The *dbi-users* mailing list has lots of experienced people who\nshould be able to help you if you need it. If you do email Tim he is very likely to just forward\nit to the mailing list.\n\nIRC\nDBI IRC Channel: #dbi on irc.perl.org ()\n\nOnline\nStackOverflow has a DBI tag with over 800\nquestions.\n\nThe DBI home page at and the DBI FAQ at may\nbe worth a visit. They include links to other resources, but *are rather out-dated*.\n\nReporting a Bug\nIf you think you've found a bug then please read \"How to Report Bugs Effectively\" by Simon\nTatham: .\n\nIf you think you've found a memory leak then read \"Memory Leaks\".\n\nYour problem is most likely related to the specific DBD driver module you're using. If that's\nthe case then click on the 'Bugs' link on the page for your driver. Only\nsubmit a bug report against the DBI itself if you're sure that your issue isn't related to the\ndriver you're using.\n\nNOTES\nThis is the DBI specification that corresponds to DBI version 1.642 (see DBI::Changes for\ndetails).\n\nThe DBI is evolving at a steady pace, so it's good to check that you have the latest copy.\n\nThe significant user-visible changes in each release are documented in the DBI::Changes module\nso you can read them by executing \"perldoc DBI::Changes\".\n\nSome DBI changes require changes in the drivers, but the drivers can take some time to catch up.\nNewer versions of the DBI have added features that may not yet be supported by the drivers you\nuse. Talk to the authors of your drivers if you need a new feature that is not yet supported.\n\nFeatures added after DBI 1.21 (February 2002) are marked in the text with the version number of\nthe DBI release they first appeared in.\n\nExtensions to the DBI API often use the \"DBIx::*\" namespace. See \"Naming Conventions and Name\nSpace\". DBI extension modules can be found at . And all\nmodules related to the DBI can be found at .\n",
"subsections": []
},
"DESCRIPTION": {
"content": "The DBI is a database access module for the Perl programming language. It defines a set of\nmethods, variables, and conventions that provide a consistent database interface, independent of\nthe actual database being used.\n\nIt is important to remember that the DBI is just an interface. The DBI is a layer of \"glue\"\nbetween an application and one or more database *driver* modules. It is the driver modules which\ndo most of the real work. The DBI provides a standard interface and framework for the drivers to\noperate within.\n\nThis document often uses terms like *references*, *objects*, *methods*. If you're not familiar\nwith those terms then it would be a good idea to read at least the following perl manuals first:\nperlreftut, perldsc, perllol, and perlboot.\n",
"subsections": [
{
"name": "Architecture of a DBI Application",
"content": "|<- Scope of DBI ->|\n.-. .--------------. .-------------.\n.-------. | |---| XYZ Driver |---| XYZ Engine |\n| Perl | | | `--------------' `-------------'\n| script| |A| |D| .--------------. .-------------.\n| using |--|P|--|B|---|Oracle Driver |---|Oracle Engine|\n| DBI | |I| |I| `--------------' `-------------'\n| API | | |...\n|methods| | |... Other drivers\n`-------' | |...\n`-'\n\nThe API, or Application Programming Interface, defines the call interface and variables for Perl\nscripts to use. The API is implemented by the Perl DBI extension.\n\nThe DBI \"dispatches\" the method calls to the appropriate driver for actual execution. The DBI is\nalso responsible for the dynamic loading of drivers, error checking and handling, providing\ndefault implementations for methods, and many other non-database specific duties.\n\nEach driver contains implementations of the DBI methods using the private interface functions of\nthe corresponding database engine. Only authors of sophisticated/multi-database applications or\ngeneric library functions need be concerned with drivers.\n"
},
{
"name": "Notation and Conventions",
"content": "The following conventions are used in this document:\n\n$dbh Database handle object\n$sth Statement handle object\n$drh Driver handle object (rarely seen or used in applications)\n$h Any of the handle types above ($dbh, $sth, or $drh)\n$rc General Return Code (boolean: true=ok, false=error)\n$rv General Return Value (typically an integer)\n@ary List of values returned from the database, typically a row of data\n$rows Number of rows processed (if available, else -1)\n$fh A filehandle\nundef NULL values are represented by undefined values in Perl\n\\%attr Reference to a hash of attribute values passed to methods\n\nNote that Perl will automatically destroy database and statement handle objects if all\nreferences to them are deleted.\n"
},
{
"name": "Outline Usage",
"content": "To use DBI, first you need to load the DBI module:\n\nuse DBI;\nuse strict;\n\n(The \"use strict;\" isn't required but is strongly recommended.)\n\nThen you need to \"connect\" to your data source and get a *handle* for that connection:\n\n$dbh = DBI->connect($dsn, $user, $password,\n{ RaiseError => 1, AutoCommit => 0 });\n\nSince connecting can be expensive, you generally just connect at the start of your program and\ndisconnect at the end.\n\nExplicitly defining the required \"AutoCommit\" behaviour is strongly recommended and may become\nmandatory in a later version. This determines whether changes are automatically committed to the\ndatabase when executed, or need to be explicitly committed later.\n\nThe DBI allows an application to \"prepare\" statements for later execution. A prepared statement\nis identified by a statement handle held in a Perl variable. We'll call the Perl variable $sth\nin our examples.\n\nThe typical method call sequence for a \"SELECT\" statement is:\n\nprepare,\nexecute, fetch, fetch, ...\nexecute, fetch, fetch, ...\nexecute, fetch, fetch, ...\n\nfor example:\n\n$sth = $dbh->prepare(\"SELECT foo, bar FROM table WHERE baz=?\");\n\n$sth->execute( $baz );\n\nwhile ( @row = $sth->fetchrowarray ) {\nprint \"@row\\n\";\n}\n\nFor queries that are not executed many times at once, it is often cleaner to use the higher\nlevel select wrappers:\n\n$rowhashref = $dbh->selectrowhashref(\"SELECT foo, bar FROM table WHERE baz=?\", undef, $baz);\n\n$arrayrefofrowhashrefs = $dbh->selectallarrayref(\n\"SELECT foo, bar FROM table WHERE baz BETWEEN ? AND ?\",\n{ Slice => {} }, $bazmin, $bazmax);\n\nThe typical method call sequence for a *non*-\"SELECT\" statement is:\n\nprepare,\nexecute,\nexecute,\nexecute.\n\nfor example:\n\n$sth = $dbh->prepare(\"INSERT INTO table(foo,bar,baz) VALUES (?,?,?)\");\n\nwhile() {\nchomp;\nmy ($foo,$bar,$baz) = split /,/;\n$sth->execute( $foo, $bar, $baz );\n}\n\nThe \"do()\" method is a wrapper of prepare and execute that can be simpler for non repeated\n*non*-\"SELECT\" statements (or with drivers that don't support placeholders):\n\n$rowsaffected = $dbh->do(\"UPDATE yourtable SET foo = foo + 1\");\n\n$rowsaffected = $dbh->do(\"DELETE FROM table WHERE foo = ?\", undef, $foo);\n\nTo commit your changes to the database (when \"AutoCommit\" is off):\n\n$dbh->commit; # or call $dbh->rollback; to undo changes\n\nFinally, when you have finished working with the data source, you should \"disconnect\" from it:\n\n$dbh->disconnect;\n\nGeneral Interface Rules & Caveats\nThe DBI does not have a concept of a \"current session\". Every session has a handle object (i.e.,\na $dbh) returned from the \"connect\" method. That handle object is used to invoke database\nrelated methods.\n\nMost data is returned to the Perl script as strings. (Null values are returned as \"undef\".) This\nallows arbitrary precision numeric data to be handled without loss of accuracy. Beware that Perl\nmay not preserve the same accuracy when the string is used as a number.\n\nDates and times are returned as character strings in the current default format of the\ncorresponding database engine. Time zone effects are database/driver dependent.\n\nPerl supports binary data in Perl strings, and the DBI will pass binary data to and from the\ndriver without change. It is up to the driver implementors to decide how they wish to handle\nsuch binary data.\n\nPerl supports two kinds of strings: Unicode (utf8 internally) and non-Unicode (defaults to\niso-8859-1 if forced to assume an encoding). Drivers should accept both kinds of strings and, if\nrequired, convert them to the character set of the database being used. Similarly, when fetching\nfrom the database character data that isn't iso-8859-1 the driver should convert it into utf8.\n\nMultiple SQL statements may not be combined in a single statement handle ($sth), although some\ndatabases and drivers do support this (notably Sybase and SQL Server).\n\nNon-sequential record reads are not supported in this version of the DBI. In other words,\nrecords can only be fetched in the order that the database returned them, and once fetched they\nare forgotten.\n\nPositioned updates and deletes are not directly supported by the DBI. See the description of the\n\"CursorName\" attribute for an alternative.\n\nIndividual driver implementors are free to provide any private functions and/or handle\nattributes that they feel are useful. Private driver functions can be invoked using the DBI\n\"func()\" method. Private driver attributes are accessed just like standard attributes.\n\nMany methods have an optional \"\\%attr\" parameter which can be used to pass information to the\ndriver implementing the method. Except where specifically documented, the \"\\%attr\" parameter can\nonly be used to pass driver specific hints. In general, you can ignore \"\\%attr\" parameters or\npass it as \"undef\".\n"
},
{
"name": "Naming Conventions and Name Space",
"content": "The DBI package and all packages below it (\"DBI::*\") are reserved for use by the DBI. Extensions\nand related modules use the \"DBIx::\" namespace (see\n). Package names beginning with \"DBD::\" are\nreserved for use by DBI database drivers. All environment variables used by the DBI or by\nindividual DBDs begin with \"\"DBI\"\" or \"\"DBD\"\".\n\nThe letter case used for attribute names is significant and plays an important part in the\nportability of DBI scripts. The case of the attribute name is used to signify who defined the\nmeaning of that name and its values.\n\nCase of name Has a meaning defined by\n------------ ------------------------\nUPPERCASE Standards, e.g., X/Open, ISO SQL92 etc (portable)\nMixedCase DBI API (portable), underscores are not used.\nlowercase Driver or database engine specific (non-portable)\n\nIt is of the utmost importance that Driver developers only use lowercase attribute names when\ndefining private attributes. Private attribute names must be prefixed with the driver name or\nsuitable abbreviation (e.g., \"\"ora\"\" for Oracle, \"\"ing\"\" for Ingres, etc).\n\nSQL - A Query Language\nMost DBI drivers require applications to use a dialect of SQL (Structured Query Language) to\ninteract with the database engine. The \"Standards Reference Information\" section provides links\nto useful information about SQL.\n\nThe DBI itself does not mandate or require any particular language to be used; it is language\nindependent. In ODBC terms, the DBI is in \"pass-thru\" mode, although individual drivers might\nnot be. The only requirement is that queries and other statements must be expressed as a single\nstring of characters passed as the first argument to the \"prepare\" or \"do\" methods.\n\nFor an interesting diversion on the *real* history of RDBMS and SQL, from the people who made it\nhappen, see:\n\nhttp://www.mcjones.org/SystemR/SQLReunion95/sqlr95.html\n\nFollow the \"Full Contents\" then \"Intergalactic dataspeak\" links for the SQL history.\n"
},
{
"name": "Placeholders and Bind Values",
"content": "Some drivers support placeholders and bind values. *Placeholders*, also called parameter\nmarkers, are used to indicate values in a database statement that will be supplied later, before\nthe prepared statement is executed. For example, an application might use the following to\ninsert a row of data into the SALES table:\n\nINSERT INTO sales (productcode, qty, price) VALUES (?, ?, ?)\n\nor the following, to select the description for a product:\n\nSELECT description FROM products WHERE productcode = ?\n\nThe \"?\" characters are the placeholders. The association of actual values with placeholders is\nknown as *binding*, and the values are referred to as *bind values*. Note that the \"?\" is not\nenclosed in quotation marks, even when the placeholder represents a string.\n\nSome drivers also allow placeholders like \":\"*name* and \":\"*N* (e.g., \":1\", \":2\", and so on) in\naddition to \"?\", but their use is not portable.\n\nIf the \":\"*N* form of placeholder is supported by the driver you're using, then you should be\nable to use either \"bindparam\" or \"execute\" to bind values. Check your driver documentation.\n\nSome drivers allow you to prevent the recognition of a placeholder by placing a single backslash\ncharacter (\"\\\") immediately before it. The driver will remove the backslash character and ignore\nthe placeholder, passing it unchanged to the backend. If the driver supports this then\n\"getinfo\"(9000) will return true.\n\nWith most drivers, placeholders can't be used for any element of a statement that would prevent\nthe database server from validating the statement and creating a query execution plan for it.\nFor example:\n\n\"SELECT name, age FROM ?\" # wrong (will probably fail)\n\"SELECT name, ? FROM people\" # wrong (but may not 'fail')\n\nAlso, placeholders can only represent single scalar values. For example, the following statement\nwon't work as expected for more than one value:\n\n\"SELECT name, age FROM people WHERE name IN (?)\" # wrong\n\"SELECT name, age FROM people WHERE name IN (?,?)\" # two names\n\nWhen using placeholders with the SQL \"LIKE\" qualifier, you must remember that the placeholder\nsubstitutes for the whole string. So you should use \"\"... LIKE ? ...\"\" and include any wildcard\ncharacters in the value that you bind to the placeholder.\n\nNULL Values\n\nUndefined values, or \"undef\", are used to indicate NULL values. You can insert and update\ncolumns with a NULL value as you would a non-NULL value. These examples insert and update the\ncolumn \"age\" with a NULL value:\n\n$sth = $dbh->prepare(qq{\nINSERT INTO people (fullname, age) VALUES (?, ?)\n});\n$sth->execute(\"Joe Bloggs\", undef);\n\n$sth = $dbh->prepare(qq{\nUPDATE people SET age = ? WHERE fullname = ?\n});\n$sth->execute(undef, \"Joe Bloggs\");\n\nHowever, care must be taken when trying to use NULL values in a \"WHERE\" clause. Consider:\n\nSELECT fullname FROM people WHERE age = ?\n\nBinding an \"undef\" (NULL) to the placeholder will *not* select rows which have a NULL \"age\"! At\nleast for database engines that conform to the SQL standard. Refer to the SQL manual for your\ndatabase engine or any SQL book for the reasons for this. To explicitly select NULLs you have to\nsay \"\"WHERE age IS NULL\"\".\n\nA common issue is to have a code fragment handle a value that could be either \"defined\" or\n\"undef\" (non-NULL or NULL) at runtime. A simple technique is to prepare the appropriate\nstatement as needed, and substitute the placeholder for non-NULL cases:\n\n$sqlclause = defined $age? \"age = ?\" : \"age IS NULL\";\n$sth = $dbh->prepare(qq{\nSELECT fullname FROM people WHERE $sqlclause\n});\n$sth->execute(defined $age ? $age : ());\n\nThe following technique illustrates qualifying a \"WHERE\" clause with several columns, whose\nassociated values (\"defined\" or \"undef\") are in a hash %h:\n\nfor my $col (\"age\", \"phone\", \"email\") {\nif (defined $h{$col}) {\npush @sqlqual, \"$col = ?\";\npush @sqlbind, $h{$col};\n}\nelse {\npush @sqlqual, \"$col IS NULL\";\n}\n}\n$sqlclause = join(\" AND \", @sqlqual);\n$sth = $dbh->prepare(qq{\nSELECT fullname FROM people WHERE $sqlclause\n});\n$sth->execute(@sqlbind);\n\nThe techniques above call prepare for the SQL statement with each call to execute. Because calls\nto prepare() can be expensive, performance can suffer when an application iterates many times\nover statements like the above.\n\nA better solution is a single \"WHERE\" clause that supports both NULL and non-NULL comparisons.\nIts SQL statement would need to be prepared only once for all cases, thus improving performance.\nSeveral examples of \"WHERE\" clauses that support this are presented below. But each example\nlacks portability, robustness, or simplicity. Whether an example is supported on your database\nengine depends on what SQL extensions it provides, and where it supports the \"?\" placeholder in\na statement.\n\n0) age = ?\n1) NVL(age, xx) = NVL(?, xx)\n2) ISNULL(age, xx) = ISNULL(?, xx)\n3) DECODE(age, ?, 1, 0) = 1\n4) age = ? OR (age IS NULL AND ? IS NULL)\n5) age = ? OR (age IS NULL AND SPISNULL(?) = 1)\n6) age = ? OR (age IS NULL AND ? = 1)\n\nStatements formed with the above \"WHERE\" clauses require execute statements as follows. The\narguments are required, whether their values are \"defined\" or \"undef\".\n\n0,1,2,3) $sth->execute($age);\n4,5) $sth->execute($age, $age);\n6) $sth->execute($age, defined($age) ? 0 : 1);\n\nExample 0 should not work (as mentioned earlier), but may work on a few database engines anyway\n(e.g. Sybase). Example 0 is part of examples 4, 5, and 6, so if example 0 works, these other\nexamples may work, even if the engine does not properly support the right hand side of the \"OR\"\nexpression.\n\nExamples 1 and 2 are not robust: they require that you provide a valid column value xx (e.g.\n'~') which is not present in any row. That means you must have some notion of what data won't be\nstored in the column, and expect clients to adhere to that.\n\nExample 5 requires that you provide a stored procedure (SPISNULL in this example) that acts as\na function: it checks whether a value is null, and returns 1 if it is, or 0 if not.\n\nExample 6, the least simple, is probably the most portable, i.e., it should work with most, if\nnot all, database engines.\n\nHere is a table that indicates which examples above are known to work on various database\nengines:\n\n-----Examples------\n0 1 2 3 4 5 6\n- - - - - - -\nOracle 9 N Y N Y Y ? Y\nInformix IDS 9 N N N Y N Y Y\nMS SQL N N Y N Y ? Y\nSybase Y N N N N N Y\nAnyData,DBM,CSV Y N N N Y Y* Y\nSQLite 3.3 N N N N Y N N\nMSAccess N N N N Y N Y\n\n* Works only because Example 0 works.\n\nDBI provides a sample perl script that will test the examples above on your database engine and\ntell you which ones work. It is located in the ex/ subdirectory of the DBI source distribution,\nor here: Please use the\nscript to help us fill-in and maintain this table.\n\nPerformance\n\nWithout using placeholders, the insert statement shown previously would have to contain the\nliteral values to be inserted and would have to be re-prepared and re-executed for each row.\nWith placeholders, the insert statement only needs to be prepared once. The bind values for each\nrow can be given to the \"execute\" method each time it's called. By avoiding the need to\nre-prepare the statement for each row, the application typically runs many times faster. Here's\nan example:\n\nmy $sth = $dbh->prepare(q{\nINSERT INTO sales (productcode, qty, price) VALUES (?, ?, ?)\n}) or die $dbh->errstr;\nwhile (<>) {\nchomp;\nmy ($productcode, $qty, $price) = split /,/;\n$sth->execute($productcode, $qty, $price) or die $dbh->errstr;\n}\n$dbh->commit or die $dbh->errstr;\n\nSee \"execute\" and \"bindparam\" for more details.\n\nThe \"q{...}\" style quoting used in this example avoids clashing with quotes that may be used in\nthe SQL statement. Use the double-quote like \"qq{...}\" operator if you want to interpolate\nvariables into the string. See \"Quote and Quote-like Operators\" in perlop for more details.\n\nSee also the \"bindcolumns\" method, which is used to associate Perl variables with the output\ncolumns of a \"SELECT\" statement.\n"
}
]
},
"THE DBI PACKAGE AND CLASS": {
"content": "In this section, we cover the DBI class methods, utility functions, and the dynamic attributes\nassociated with generic DBI handles.\n\nDBI Constants\nConstants representing the values of the SQL standard types can be imported individually by\nname, or all together by importing the special \":sqltypes\" tag.\n\nThe names and values of all the defined SQL standard types can be produced like this:\n\nforeach (@{ $DBI::EXPORTTAGS{sqltypes} }) {\nprintf \"%s=%d\\n\", $, &{\"DBI::$\"};\n}\n\nThese constants are defined by SQL/CLI, ODBC or both. \"SQLBIGINT\" has conflicting codes in\nSQL/CLI and ODBC, DBI uses the ODBC one.\n\nSee the \"typeinfo\", \"typeinfoall\", and \"bindparam\" methods for possible uses.\n\nNote that just because the DBI defines a named constant for a given data type doesn't mean that\ndrivers will support that data type.\n\nDBI Class Methods\nThe following methods are provided by the DBI class:\n\n\"parsedsn\"\n($scheme, $driver, $attrstring, $attrhash, $driverdsn) = DBI->parsedsn($dsn)\nor die \"Can't parse DBI DSN '$dsn'\";\n\nBreaks apart a DBI Data Source Name (DSN) and returns the individual parts. If $dsn doesn't\ncontain a valid DSN then parsedsn() returns an empty list.\n\n$scheme is the first part of the DSN and is currently always 'dbi'. $driver is the driver name,\npossibly defaulted to $ENV{DBIDRIVER}, and may be undefined. $attrstring is the contents of\nthe optional attribute string, which may be undefined. If $attrstring is not empty then\n$attrhash is a reference to a hash containing the parsed attribute names and values.\n$driverdsn is the last part of the DBI DSN string. For example:\n\n($scheme, $driver, $attrstring, $attrhash, $driverdsn)\n= DBI->parsedsn(\"dbi:MyDriver(RaiseError=>1):db=test;port=42\");\n$scheme = 'dbi';\n$driver = 'MyDriver';\n$attrstring = 'RaiseError=>1';\n$attrhash = { 'RaiseError' => '1' };\n$driverdsn = 'db=test;port=42';\n\nThe parsedsn() method was added in DBI 1.43.\n\n\"connect\"\n$dbh = DBI->connect($datasource, $username, $password)\nor die $DBI::errstr;\n$dbh = DBI->connect($datasource, $username, $password, \\%attr)\nor die $DBI::errstr;\n\nEstablishes a database connection, or session, to the requested $datasource. Returns a database\nhandle object if the connection succeeds. Use \"$dbh->disconnect\" to terminate the connection.\n\nIf the connect fails (see below), it returns \"undef\" and sets both $DBI::err and $DBI::errstr.\n(It does *not* explicitly set $!.) You should generally test the return status of \"connect\" and\n\"print $DBI::errstr\" if it has failed.\n\nMultiple simultaneous connections to multiple databases through multiple drivers can be made via\nthe DBI. Simply make one \"connect\" call for each database and keep a copy of each returned\ndatabase handle.\n\nThe $datasource value must begin with \"\"dbi:\"*drivername*\":\"\". The *drivername* specifies the\ndriver that will be used to make the connection. (Letter case is significant.)\n\nAs a convenience, if the $datasource parameter is undefined or empty, the DBI will substitute\nthe value of the environment variable \"DBIDSN\". If just the *drivername* part is empty (i.e.,\nthe $datasource prefix is \"\"dbi::\"\"), the environment variable \"DBIDRIVER\" is used. If neither\nvariable is set, then \"connect\" dies.\n\nExamples of $datasource values are:\n\ndbi:DriverName:databasename\ndbi:DriverName:databasename@hostname:port\ndbi:DriverName:database=databasename;host=hostname;port=port\n\nThere is *no standard* for the text following the driver name. Each driver is free to use\nwhatever syntax it wants. The only requirement the DBI makes is that all the information is\nsupplied in a single string. You must consult the documentation for the drivers you are using\nfor a description of the syntax they require.\n\nIt is recommended that drivers support the ODBC style, shown in the last example above. It is\nalso recommended that they support the three common names '\"host\"', '\"port\"', and '\"database\"'\n(plus '\"db\"' as an alias for \"database\"). This simplifies automatic construction of basic DSNs:\n\"dbi:$driver:database=$db;host=$host;port=$port\". Drivers should aim to 'do something\nreasonable' when given a DSN in this form, but if any part is meaningless for that driver (such\nas 'port' for Informix) it should generate an error if that part is not empty.\n\nIf the environment variable \"DBIAUTOPROXY\" is defined (and the driver in $datasource is not\n\"\"Proxy\"\") then the connect request will automatically be changed to:\n\n$ENV{DBIAUTOPROXY};dsn=$datasource\n\n\"DBIAUTOPROXY\" is typically set as \"\"dbi:Proxy:hostname=...;port=...\"\". If $ENV{DBIAUTOPROXY}\ndoesn't begin with '\"dbi:\"' then \"dbi:Proxy:\" will be prepended to it first. See the DBD::Proxy\ndocumentation for more details.\n\nIf $username or $password are undefined (rather than just empty), then the DBI will substitute\nthe values of the \"DBIUSER\" and \"DBIPASS\" environment variables, respectively. The DBI will\nwarn if the environment variables are not defined. However, the everyday use of these\nenvironment variables is not recommended for security reasons. The mechanism is primarily\nintended to simplify testing. See below for alternative way to specify the username and\npassword.\n\n\"DBI->connect\" automatically installs the driver if it has not been installed yet. Driver\ninstallation either returns a valid driver handle, or it *dies* with an error message that\nincludes the string \"\"installdriver\"\" and the underlying problem. So \"DBI->connect\" will die on\na driver installation failure and will only return \"undef\" on a connect failure, in which case\n$DBI::errstr will hold the error message. Use \"eval\" if you need to catch the \"\"installdriver\"\"\nerror.\n\nThe $datasource argument (with the \"\"dbi:...:\"\" prefix removed) and the $username and $password\narguments are then passed to the driver for processing. The DBI does not define any\ninterpretation for the contents of these fields. The driver is free to interpret the\n$datasource, $username, and $password fields in any way, and supply whatever defaults are\nappropriate for the engine being accessed. (Oracle, for example, uses the ORACLESID and\nTWOTASK environment variables if no $datasource is specified.)\n\nThe \"AutoCommit\" and \"PrintError\" attributes for each connection default to \"on\". (See\n\"AutoCommit\" and \"PrintError\" for more information.) However, it is strongly recommended that\nyou explicitly define \"AutoCommit\" rather than rely on the default. The \"PrintWarn\" attribute\ndefaults to true. The \"RaiseWarn\" attribute defaults to false.\n\nThe \"\\%attr\" parameter can be used to alter the default settings of \"PrintError\", \"RaiseError\",\n\"AutoCommit\", and other attributes. For example:\n\n$dbh = DBI->connect($datasource, $user, $pass, {\nPrintError => 0,\nAutoCommit => 0\n});\n\nThe username and password can also be specified using the attributes \"Username\" and \"Password\",\nin which case they take precedence over the $username and $password parameters.\n\nYou can also define connection attribute values within the $datasource parameter. For example:\n\ndbi:DriverName(PrintWarn=>0,PrintError=>0,Taint=>1):...\n\nIndividual attributes values specified in this way take precedence over any conflicting values\nspecified via the \"\\%attr\" parameter to \"connect\".\n\nThe \"dbiconnectmethod\" attribute can be used to specify which driver method should be called\nto establish the connection. The only useful values are 'connect', 'connectcached', or some\nspecialized case like 'Apache::DBI::connect' (which is automatically the default when running\nwithin Apache).\n\nWhere possible, each session ($dbh) is independent from the transactions in other sessions. This\nis useful when you need to hold cursors open across transactions--for example, if you use one\nsession for your long lifespan cursors (typically read-only) and another for your short update\ntransactions.\n\nFor compatibility with old DBI scripts, the driver can be specified by passing its name as the\nfourth argument to \"connect\" (instead of \"\\%attr\"):\n\n$dbh = DBI->connect($datasource, $user, $pass, $driver);\n\nIn this \"old-style\" form of \"connect\", the $datasource should not start with\n\"\"dbi:drivername:\"\". (If it does, the embedded drivername will be ignored). Also note that in\nthis older form of \"connect\", the \"$dbh->{AutoCommit}\" attribute is *undefined*, the\n\"$dbh->{PrintError}\" attribute is off, and the old \"DBIDBNAME\" environment variable is checked\nif \"DBIDSN\" is not defined. Beware that this \"old-style\" \"connect\" will soon be withdrawn in a\nfuture version of DBI.\n\n\"connectcached\"\n$dbh = DBI->connectcached($datasource, $username, $password)\nor die $DBI::errstr;\n$dbh = DBI->connectcached($datasource, $username, $password, \\%attr)\nor die $DBI::errstr;\n\n\"connectcached\" is like \"connect\", except that the database handle returned is also stored in a\nhash associated with the given parameters. If another call is made to \"connectcached\" with the\nsame parameter values, then the corresponding cached $dbh will be returned if it is still valid.\nThe cached database handle is replaced with a new connection if it has been disconnected or if\nthe \"ping\" method fails.\n\nNote that the behaviour of this method differs in several respects from the behaviour of\npersistent connections implemented by Apache::DBI. However, if Apache::DBI is loaded then\n\"connectcached\" will use it.\n\nCaching connections can be useful in some applications, but it can also cause problems, such as\ntoo many connections, and so should be used with care. In particular, avoid changing the\nattributes of a database handle created via connectcached() because it will affect other code\nthat may be using the same handle. When connectcached() returns a handle the attributes will be\nreset to their initial values. This can cause problems, especially with the \"AutoCommit\"\nattribute.\n\nAlso, to ensure that the attributes passed are always the same, avoid passing references inline.\nFor example, the \"Callbacks\" attribute is specified as a hash reference. Be sure to declare it\nexternal to the call to connectcached(), such that the hash reference is not re-created on\nevery call. A package-level lexical works well:\n\npackage MyDBH;\nmy $cb = {\n'connectcached.reused' => sub { delete $[4]->{AutoCommit} },\n};\n\nsub dbh {\nDBI->connectcached( $dsn, $username, $auth, { Callbacks => $cb });\n}\n\nWhere multiple separate parts of a program are using connectcached() to connect to the same\ndatabase with the same (initial) attributes it is a good idea to add a private attribute to the",
"subsections": [
{
"name": "connect_cached",
"content": "DBI->connectcached(..., { privatefoocachekey => \"Bar\", ... });\n\nHandles returned from that connectcached() call will only be returned by other connectcached()\ncall elsewhere in the code if those other calls also pass in the same attribute values,\nincluding the private one. (I've used \"privatefoocachekey\" here as an example, you can use any\nattribute name with a \"private\" prefix.)\n\nTaking that one step further, you can limit a particular connectcached() call to return handles\nunique to that one place in the code by setting the private attribute to a unique value for that\nplace:\n\nDBI->connectcached(..., { privatefoocachekey => FILE.LINE, ... });\n\nBy using a private attribute you still get connection caching for the individual calls to"
},
{
"name": "connect_cached",
"content": "the database handles are isolated from any attribute changes made to other handles.\n\nThe cache can be accessed (and cleared) via the \"CachedKids\" attribute:\n\nmy $CachedKidshashref = $dbh->{Driver}->{CachedKids};\n%$CachedKidshashref = () if $CachedKidshashref;\n\n\"availabledrivers\"\n@ary = DBI->availabledrivers;\n@ary = DBI->availabledrivers($quiet);\n\nReturns a list of all available drivers by searching for \"DBD::*\" modules through the\ndirectories in @INC. By default, a warning is given if some drivers are hidden by others of the\nsame name in earlier directories. Passing a true value for $quiet will inhibit the warning.\n\n\"installeddrivers\"\n%drivers = DBI->installeddrivers();\n\nReturns a list of driver name and driver handle pairs for all drivers 'installed' (loaded) into\nthe current process. The driver name does not include the 'DBD::' prefix.\n\nTo get a list of all drivers available in your perl installation you can use\n\"availabledrivers\".\n\nAdded in DBI 1.49.\n\n\"installedversions\"\nDBI->installedversions;\n@ary = DBI->installedversions;\n$hash = DBI->installedversions;\n\nCalls availabledrivers() and attempts to load each of them in turn using installdriver(). For\neach load that succeeds the driver name and version number are added to a hash. When running\nunder DBI::PurePerl drivers which appear not be pure-perl are ignored.\n\nWhen called in array context the list of successfully loaded drivers is returned (without the\n'DBD::' prefix).\n\nWhen called in scalar context an extra entry for the \"DBI\" is added (and \"DBI::PurePerl\" if\nappropriate) and a reference to the hash is returned.\n\nWhen called in a void context the installedversions() method will print out a formatted list of\nthe hash contents, one per line, along with some other information about the DBI version and OS.\n\nDue to the potentially high memory cost and unknown risks of loading in an unknown number of\ndrivers that just happen to be installed on the system, this method is not recommended for\ngeneral use. Use availabledrivers() instead.\n\nThe installedversions() method is primarily intended as a quick way to see from the command\nline what's installed. For example:\n\nperl -MDBI -e 'DBI->installedversions'\n\nThe installedversions() method was added in DBI 1.38.\n\n\"datasources\"\n@ary = DBI->datasources($driver);\n@ary = DBI->datasources($driver, \\%attr);\n\nReturns a list of data sources (databases) available via the named driver. If $driver is empty\nor \"undef\", then the value of the \"DBIDRIVER\" environment variable is used.\n\nThe driver will be loaded if it hasn't been already. Note that if the driver loading fails then"
},
{
"name": "data_sources",
"content": "underlying problem.\n\nData sources are returned in a form suitable for passing to the \"connect\" method (that is, they\nwill include the \"\"dbi:$driver:\"\" prefix).\n\nNote that many drivers have no way of knowing what data sources might be available for it. These\ndrivers return an empty or incomplete list or may require driver-specific attributes.\n\nThere is also a datasources() method defined for database handles.\n\n\"trace\"\nDBI->trace($tracesetting)\nDBI->trace($tracesetting, $tracefilename)\nDBI->trace($tracesetting, $tracefilehandle)\n$tracesetting = DBI->trace;\n\nThe \"DBI->trace\" method sets the *global default* trace settings and returns the *previous*\ntrace settings. It can also be used to change where the trace output is sent.\n\nThere's a similar method, \"$h->trace\", which sets the trace settings for the specific handle\nit's called on.\n\nSee the \"TRACING\" section for full details about the DBI's powerful tracing facilities.\n\n\"visithandles\"\nDBI->visithandles( $coderef );\nDBI->visithandles( $coderef, $info );\n\nWhere $coderef is a reference to a subroutine and $info is an arbitrary value which, if\nundefined, defaults to a reference to an empty hash. Returns $info.\n\nFor each installed driver handle, if any, $coderef is invoked as:\n\n$coderef->($driverhandle, $info);\n\nIf the execution of $coderef returns a true value then \"visitchildhandles\" is called on that\nchild handle and passed the returned value as $info.\n\nFor example:\n\nmy $info = $dbh->{Driver}->visitchildhandles(sub {\nmy ($h, $info) = @;\n++$info->{ $h->{Type} }; # count types of handles (dr/db/st)\nreturn $info; # visit kids\n});\n\nSee also \"visitchildhandles\".\n\nDBI Utility Functions\nIn addition to the DBI methods listed in the previous section, the DBI package also provides\nseveral utility functions.\n\nThese can be imported into your code by listing them in the \"use\" statement. For example:\n\nuse DBI qw(neat datadiff);\n\nAlternatively, all these utility functions (except hash) can be imported using the \":utils\"\nimport tag. For example:\n\nuse DBI qw(:utils);\n\n\"datastringdesc\"\n$description = datastringdesc($string);\n\nReturns an informal description of the string. For example:\n\nUTF8 off, ASCII, 42 characters 42 bytes\nUTF8 off, non-ASCII, 42 characters 42 bytes\nUTF8 on, non-ASCII, 4 characters 6 bytes\nUTF8 on but INVALID encoding, non-ASCII, 4 characters 6 bytes\nUTF8 off, undef\n\nThe initial \"UTF8\" on/off refers to Perl's internal SvUTF8 flag. If $string has the SvUTF8 flag\nset but the sequence of bytes it contains are not a valid UTF-8 encoding then datastringdesc()\nwill report \"UTF8 on but INVALID encoding\".\n\nThe \"ASCII\" vs \"non-ASCII\" portion shows \"ASCII\" if *all* the characters in the string are ASCII\n(have code points <= 127).\n\nThe datastringdesc() function was added in DBI 1.46.\n\n\"datastringdiff\"\n$diff = datastringdiff($a, $b);\n\nReturns an informal description of the first character difference between the strings. If both\n$a and $b contain the same sequence of characters then datastringdiff() returns an empty\nstring. For example:\n\nParams a & b Result\n------------ ------\n'aaa', 'aaa' ''\n'aaa', 'abc' 'Strings differ at index 2: a[2]=a, b[2]=b'\n'aaa', undef 'String b is undef, string a has 3 characters'\n'aaa', 'aa' 'String b truncated after 2 characters'\n\nUnicode characters are reported in \"\\x{XXXX}\" format. Unicode code points in the range U+0800 to\nU+08FF are unassigned and most likely to occur due to double-encoding. Characters in this range\nare reported as \"\\x{08XX}='C'\" where \"C\" is the corresponding latin-1 character.\n\nThe datastringdiff() function only considers logical *characters* and not the underlying\nencoding. See \"datadiff\" for an alternative.\n\nThe datastringdiff() function was added in DBI 1.46.\n\n\"datadiff\"\n$diff = datadiff($a, $b);\n$diff = datadiff($a, $b, $logical);\n\nReturns an informal description of the difference between two strings. It calls\n\"datastringdesc\" and \"datastringdiff\" and returns the combined results as a multi-line\nstring.\n\nFor example, \"datadiff(\"abc\", \"ab\\x{263a}\")\" will return:\n\na: UTF8 off, ASCII, 3 characters 3 bytes\nb: UTF8 on, non-ASCII, 3 characters 5 bytes\nStrings differ at index 2: a[2]=c, b[2]=\\x{263A}\n\nIf $a and $b are identical in both the characters they contain *and* their physical encoding\nthen datadiff() returns an empty string. If $logical is true then physical encoding differences\nare ignored (but are still reported if there is a difference in the characters).\n\nThe datadiff() function was added in DBI 1.46.\n\n\"neat\"\n$str = neat($value);\n$str = neat($value, $maxlen);\n\nReturn a string containing a neat (and tidy) representation of the supplied value.\n\nStrings will be quoted, although internal quotes will *not* be escaped. Values known to be\nnumeric will be unquoted. Undefined (NULL) values will be shown as \"undef\" (without quotes).\n\nIf the string is flagged internally as utf8 then double quotes will be used, otherwise single\nquotes are used and unprintable characters will be replaced by dot (.).\n\nFor result strings longer than $maxlen the result string will be truncated to \"$maxlen-4\" and\n\"\"...'\"\" will be appended. If $maxlen is 0 or \"undef\", it defaults to $DBI::neatmaxlen which,\nin turn, defaults to 400.\n\nThis function is designed to format values for human consumption. It is used internally by the\nDBI for \"trace\" output. It should typically *not* be used for formatting values for database\nuse. (See also \"quote\".)\n\n\"neatlist\"\n$str = neatlist(\\@listref, $maxlen, $fieldsep);\n\nCalls \"neat\" on each element of the list and returns a string containing the results joined with\n$fieldsep. $fieldsep defaults to \", \".\n\n\"lookslikenumber\"\n@bool = lookslikenumber(@array);\n\nReturns true for each element that looks like a number. Returns false for each element that does\nnot look like a number. Returns \"undef\" for each element that is undefined or empty.\n\n\"hash\"\n$hashvalue = DBI::hash($buffer, $type);\n\nReturn a 32-bit integer 'hash' value corresponding to the contents of $buffer. The $type\nparameter selects which kind of hash algorithm should be used.\n\nFor the technically curious, type 0 (which is the default if $type isn't specified) is based on\nthe Perl 5.1 hash except that the value is forced to be negative (for obscure historical\nreasons). Type 1 is the better \"Fowler / Noll / Vo\" (FNV) hash. See\n for more information. Both types are implemented in\nC and are very fast.\n\nThis function doesn't have much to do with databases, except that it can sometimes be handy to\nstore such values in a database. It also doesn't have much to do with perl hashes, like %foo.\n\n\"sqltypecast\"\n$sts = DBI::sqltypecast($sv, $sqltype, $flags);\n\nsqltypecast attempts to cast $sv to the SQL type (see DBI Constants) specified in $sqltype.\nAt present only the SQL types \"SQLINTEGER\", \"SQLDOUBLE\" and \"SQLNUMERIC\" are supported.\n\nFor \"SQLINTEGER\" the effect is similar to using the value in an expression that requires an\ninteger. It gives the perl scalar an 'integer aspect'. (Technically the value gains an IV, or\npossibly a UV or NV if the value is too large for an IV.)\n\nFor \"SQLDOUBLE\" the effect is similar to using the value in an expression that requires a\ngeneral numeric value. It gives the perl scalar a 'numeric aspect'. (Technically the value gains\nan NV.)\n\n\"SQLNUMERIC\" is similar to \"SQLINTEGER\" or \"SQLDOUBLE\" but more general and more cautious. It\nwill look at the string first and if it looks like an integer (that will fit in an IV or UV) it\nwill act like \"SQLINTEGER\", if it looks like a floating point value it will act like\n\"SQLDOUBLE\", if it looks like neither then it will do nothing - and thereby avoid the warnings\nthat would be generated by \"SQLINTEGER\" and \"SQLDOUBLE\" when given non-numeric data.\n\n$flags may be:\n\n\"DBIstcfDISCARDSTRING\"\nIf this flag is specified then when the driver successfully casts the bound perl scalar to a\nnon-string type then the string portion of the scalar will be discarded.\n\n\"DBIstcfSTRICT\"\nIf $sv cannot be cast to the requested $sqltype then by default it is left untouched and no\nerror is generated. If you specify \"DBIstcfSTRICT\" and the cast fails, this will generate\nan error.\n\nThe returned $sts value is:\n\n-2 sqltype is not handled\n-1 sv is undef so unchanged\n0 sv could not be cast cleanly and DBIstcfSTRICT was used\n1 sv could not be cast and DBIstcfSTRICT was not used\n2 sv was cast successfully\n\nThis method is exported by the :utils tag and was introduced in DBI 1.611.\n\nDBI Dynamic Attributes\nDynamic attributes are always associated with the *last handle used* (that handle is represented\nby $h in the descriptions below).\n\nWhere an attribute is equivalent to a method call, then refer to the method call for all related\ndocumentation.\n\nWarning: these attributes are provided as a convenience but they do have limitations.\nSpecifically, they have a short lifespan: because they are associated with the last handle used,\nthey should only be used *immediately* after calling the method that \"sets\" them. If in any\ndoubt, use the corresponding method call.\n\n$DBI::err\nEquivalent to \"$h->err\".\n\n$DBI::errstr\nEquivalent to \"$h->errstr\".\n\n$DBI::state\nEquivalent to \"$h->state\".\n\n$DBI::rows\nEquivalent to \"$h->rows\". Please refer to the documentation for the \"rows\" method.\n\n$DBI::lasth\nReturns the DBI object handle used for the most recent DBI method call. If the last DBI method\ncall was a DESTROY then $DBI::lasth will return the handle of the parent of the destroyed\nhandle, if there is one.\n"
}
]
},
"METHODS COMMON TO ALL HANDLES": {
"content": "The following methods can be used by all types of DBI handles.\n\n\"err\"\n$rv = $h->err;\n\nReturns the *native* database engine error code from the last driver method called. The code is\ntypically an integer but you should not assume that.\n\nThe DBI resets $h->err to undef before almost all DBI method calls, so the value only has a\nshort lifespan. Also, for most drivers, the statement handles share the same error variable as\nthe parent database handle, so calling a method on one handle may reset the error on the related\nhandles.\n\n(Methods which don't reset err before being called include err() and errstr(), obviously,",
"subsections": [
{
"name": "state",
"content": "STORE() methods.)\n\nIf you need to test for specific error conditions *and* have your program be portable to\ndifferent database engines, then you'll need to determine what the corresponding error codes are\nfor all those engines and test for all of them.\n\nThe DBI uses the value of $DBI::stderr as the \"err\" value for internal errors. Drivers should\nalso do likewise. The default value for $DBI::stderr is 2000000000.\n\nA driver may return 0 from err() to indicate a warning condition after a method call. Similarly,\na driver may return an empty string to indicate a 'success with information' condition. In both\nthese cases the value is false but not undef. The errstr() and state() methods may be used to\nretrieve extra information in these cases.\n\nSee \"seterr\" for more information.\n\n\"errstr\"\n$str = $h->errstr;\n\nReturns the native database engine error message from the last DBI method called. This has the\nsame lifespan issues as the \"err\" method described above.\n\nThe returned string may contain multiple messages separated by newline characters.\n\nThe errstr() method should not be used to test for errors, use err() for that, because drivers\nmay return 'success with information' or warning messages via errstr() for methods that have not\n'failed'.\n\nSee \"seterr\" for more information.\n\n\"state\"\n$str = $h->state;\n\nReturns a state code in the standard SQLSTATE five character format. Note that the specific\nsuccess code 00000 is translated to any empty string (false). If the driver does not support\nSQLSTATE (and most don't), then state() will return \"S1000\" (General Error) for all errors.\n\nThe driver is free to return any value via \"state\", e.g., warning codes, even if it has not\ndeclared an error by returning a true value via the \"err\" method described above.\n\nThe state() method should not be used to test for errors, use err() for that, because drivers\nmay return a 'success with information' or warning state code via state() for methods that have\nnot 'failed'.\n\n\"seterr\"\n$rv = $h->seterr($err, $errstr);\n$rv = $h->seterr($err, $errstr, $state);\n$rv = $h->seterr($err, $errstr, $state, $method);\n$rv = $h->seterr($err, $errstr, $state, $method, $rv);\n\nSet the \"err\", \"errstr\", and \"state\" values for the handle. This method is typically only used\nby DBI drivers and DBI subclasses.\n\nIf the \"HandleSetErr\" attribute holds a reference to a subroutine it is called first. The\nsubroutine can alter the $err, $errstr, $state, and $method values. See \"HandleSetErr\" for full\ndetails. If the subroutine returns a true value then the handle \"err\", \"errstr\", and \"state\"\nvalues are not altered and seterr() returns an empty list (it normally returns $rv which\ndefaults to undef, see below).\n\nSetting \"err\" to a *true* value indicates an error and will trigger the normal DBI error\nhandling mechanisms, such as \"RaiseError\" and \"HandleError\", if they are enabled, when execution\nreturns from the DBI back to the application.\n\nSetting \"err\" to \"\" indicates an 'information' state, and setting it to \"0\" indicates a\n'warning' state. Setting \"err\" to \"undef\" also sets \"errstr\" to undef, and \"state\" to \"\",\nirrespective of the values of the $errstr and $state parameters.\n\nThe $method parameter provides an alternate method name for the\n\"RaiseError\"/\"PrintError\"/\"RaiseWarn\"/\"PrintWarn\" error string instead of the fairly unhelpful\n'\"seterr\"'.\n\nThe \"seterr\" method normally returns undef. The $rv parameter provides an alternate return\nvalue.\n\nSome special rules apply if the \"err\" or \"errstr\" values for the handle are *already* set...\n\nIf \"errstr\" is true then: \"\" [err was %s now %s]\"\" is appended if $err is true and \"err\" is\nalready true and the new err value differs from the original one. Similarly \"\" [state was %s now\n%s]\"\" is appended if $state is true and \"state\" is already true and the new state value differs\nfrom the original one. Finally \"\"\\n\"\" and the new $errstr are appended if $errstr differs from\nthe existing errstr value. Obviously the %s's above are replaced by the corresponding values.\n\nThe handle \"err\" value is set to $err if: $err is true; or handle \"err\" value is undef; or $err\nis defined and the length is greater than the handle \"err\" length. The effect is that an\n'information' state only overrides undef; a 'warning' overrides undef or 'information', and an\n'error' state overrides anything.\n\nThe handle \"state\" value is set to $state if $state is true and the handle \"err\" value was set\n(by the rules above).\n\nSupport for warning and information states was added in DBI 1.41.\n\n\"trace\"\n$h->trace($tracesettings);\n$h->trace($tracesettings, $tracefilename);\n$tracesettings = $h->trace;\n\nThe trace() method is used to alter the trace settings for a handle (and any future children of\nthat handle). It can also be used to change where the trace output is sent.\n\nThere's a similar method, \"DBI->trace\", which sets the global default trace settings.\n\nSee the \"TRACING\" section for full details about the DBI's powerful tracing facilities.\n\n\"tracemsg\"\n$h->tracemsg($messagetext);\n$h->tracemsg($messagetext, $minlevel);\n\nWrites $messagetext to the trace file if the trace level is greater than or equal to $minlevel\n(which defaults to 1). Can also be called as \"DBI->tracemsg($msg)\".\n\nSee \"TRACING\" for more details.\n\n\"func\"\n$h->func(@funcarguments, $funcname) or die ...;\n\nThe \"func\" method can be used to call private non-standard and non-portable methods implemented\nby the driver. Note that the function name is given as the *last* argument.\n\nIt's also important to note that the func() method does not clear a previous error ($DBI::err\netc.) and it does not trigger automatic error detection (RaiseError etc.) so you must check the\nreturn status and/or $h->err to detect errors.\n\n(This method is not directly related to calling stored procedures. Calling stored procedures is\ncurrently not defined by the DBI. Some drivers, such as DBD::Oracle, support it in non-portable\nways. See driver documentation for more details.)\n\nSee also installmethod() in DBI::DBD for how you can avoid needing to use func() and gain\ndirect access to driver-private methods.\n\n\"can\"\n$isimplemented = $h->can($methodname);\n\nReturns true if $methodname is implemented by the driver or a default method is provided by the\nDBI's driver base class. It returns false where a driver hasn't implemented a method and the\ndefault method is provided by the DBI's driver base class is just an empty stub.\n\n\"parsetraceflags\"\n$tracesettingsinteger = $h->parsetraceflags($tracesettings);\n\nParses a string containing trace settings and returns the corresponding integer value used\ninternally by the DBI and drivers.\n\nThe $tracesettings argument is a string containing a trace level between 0 and 15 and/or trace\nflag names separated by vertical bar (\"\"|\"\") or comma (\"\",\"\") characters. For example:\n\"SQL|3|foo\".\n\nIt uses the parsetraceflag() method, described below, to process the individual trace flag\nnames.\n\nThe parsetraceflags() method was added in DBI 1.42.\n\n\"parsetraceflag\"\n$bitflag = $h->parsetraceflag($traceflagname);\n\nReturns the bit flag corresponding to the trace flag name in $traceflagname. Drivers are\nexpected to override this method and check if $traceflagname is a driver specific trace flags\nand, if not, then call the DBI's default parsetraceflag().\n\nThe parsetraceflag() method was added in DBI 1.42.\n\n\"privateattributeinfo\"\n$hashref = $h->privateattributeinfo();\n\nReturns a reference to a hash whose keys are the names of driver-private handle attributes\navailable for the kind of handle (driver, database, statement) that the method was called on.\n\nFor example, the return value when called with a DBD::Sybase $dbh could look like this:\n\n{\nsybdynamicsupported => undef,\nsybocversion => undef,\nsybserverversion => undef,\nsybserverversionstring => undef,\n}\n\nand when called with a DBD::Sybase $sth they could look like this:\n\n{\nsybtypes => undef,\nsybprocstatus => undef,\nsybresulttype => undef,\n}\n\nThe values should be undef. Meanings may be assigned to particular values in future.\n\n\"swapinnerhandle\"\n$rc = $h1->swapinnerhandle( $h2 );\n$rc = $h1->swapinnerhandle( $h2, $allowreparent );\n\nBrain transplants for handles. You don't need to know about this unless you want to become a\nhandle surgeon.\n\nA DBI handle is a reference to a tied hash. A tied hash has an *inner* hash that actually holds\nthe contents. The swapinnerhandle() method swaps the inner hashes between two handles. The $h1\nand $h2 handles still point to the same tied hashes, but what those hashes are tied to has been\nswapped. In effect $h1 *becomes* $h2 and vice-versa. This is powerful stuff, expect problems.\nUse with care.\n\nAs a small safety measure, the two handles, $h1 and $h2, have to share the same parent unless\n$allowreparent is true.\n\nThe swapinnerhandle() method was added in DBI 1.44.\n\nHere's a quick kind of 'diagram' as a worked example to help think about what's happening:\n\nOriginal state:\ndbh1o -> dbh1i\nsthAo -> sthAi(dbh1i)\ndbh2o -> dbh2i\n\nswapinnerhandle dbh1o with dbh2o:\ndbh2o -> dbh1i\nsthAo -> sthAi(dbh1i)\ndbh1o -> dbh2i\n\ncreate new sth from dbh1o:\ndbh2o -> dbh1i\nsthAo -> sthAi(dbh1i)\ndbh1o -> dbh2i\nsthBo -> sthBi(dbh2i)\n\nswapinnerhandle sthAo with sthBo:\ndbh2o -> dbh1i\nsthBo -> sthAi(dbh1i)\ndbh1o -> dbh2i\nsthAo -> sthBi(dbh2i)\n\n\"visitchildhandles\"\n$h->visitchildhandles( $coderef );\n$h->visitchildhandles( $coderef, $info );\n\nWhere $coderef is a reference to a subroutine and $info is an arbitrary value which, if\nundefined, defaults to a reference to an empty hash. Returns $info.\n\nFor each child handle of $h, if any, $coderef is invoked as:\n\n$coderef->($childhandle, $info);\n\nIf the execution of $coderef returns a true value then \"visitchildhandles\" is called on that\nchild handle and passed the returned value as $info.\n\nFor example:\n\n# count database connections with names (DSN) matching a pattern\nmy $connections = 0;\n$dbh->{Driver}->visitchildhandles(sub {\nmy ($h, $info) = @;\n++$connections if $h->{Name} =~ /foo/;\nreturn 0; # don't visit kids\n})\n\nSee also \"visithandles\".\n"
}
]
},
"ATTRIBUTES COMMON TO ALL HANDLES": {
"content": "These attributes are common to all types of DBI handles.\n\nSome attributes are inherited by child handles. That is, the value of an inherited attribute in\na newly created statement handle is the same as the value in the parent database handle. Changes\nto attributes in the new statement handle do not affect the parent database handle and changes\nto the database handle do not affect existing statement handles, only future ones.\n\nAttempting to set or get the value of an unknown attribute generates a warning, except for\nprivate driver specific attributes (which all have names starting with a lowercase letter).\n\nExample:\n\n$h->{AttributeName} = ...; # set/write\n... = $h->{AttributeName}; # get/read\n\n\"Warn\"\nType: boolean, inherited\n\nThe \"Warn\" attribute enables useful warnings for certain bad practices. It is enabled by default\nand should only be disabled in rare circumstances. Since warnings are generated using the Perl\n\"warn\" function, they can be intercepted using the Perl $SIG{WARN} hook.\n\nThe \"Warn\" attribute is not related to the \"PrintWarn\" attribute.\n\n\"Active\"\nType: boolean, read-only\n\nThe \"Active\" attribute is true if the handle object is \"active\". This is rarely used in\napplications. The exact meaning of active is somewhat vague at the moment. For a database handle\nit typically means that the handle is connected to a database (\"$dbh->disconnect\" sets \"Active\"\noff). For a statement handle it typically means that the handle is a \"SELECT\" that may have more\ndata to fetch. (Fetching all the data or calling \"$sth->finish\" sets \"Active\" off.)\n\n\"Executed\"\nType: boolean\n\nThe \"Executed\" attribute is true if the handle object has been \"executed\". Currently only the\n$dbh do() method and the $sth execute(), executearray(), and executeforfetch() methods set\nthe \"Executed\" attribute.\n\nWhen it's set on a handle it is also set on the parent handle at the same time. So calling",
"subsections": [
{
"name": "execute",
"content": "The \"Executed\" attribute for a database handle is cleared by the commit() and rollback() methods\n(even if they fail). The \"Executed\" attribute of a statement handle is not cleared by the DBI\nunder any circumstances and so acts as a permanent record of whether the statement handle was\never used.\n\nThe \"Executed\" attribute was added in DBI 1.41.\n\n\"Kids\"\nType: integer, read-only\n\nFor a driver handle, \"Kids\" is the number of currently existing database handles that were\ncreated from that driver handle. For a database handle, \"Kids\" is the number of currently\nexisting statement handles that were created from that database handle. For a statement handle,\nthe value is zero.\n\n\"ActiveKids\"\nType: integer, read-only\n\nLike \"Kids\", but only counting those that are \"Active\" (as above).\n\n\"CachedKids\"\nType: hash ref\n\nFor a database handle, \"CachedKids\" returns a reference to the cache (hash) of statement handles\ncreated by the \"preparecached\" method. For a driver handle, returns a reference to the cache\n(hash) of database handles created by the \"connectcached\" method.\n\n\"Type\"\nType: scalar, read-only\n\nThe \"Type\" attribute identifies the type of a DBI handle. Returns \"dr\" for driver handles, \"db\"\nfor database handles and \"st\" for statement handles.\n\n\"ChildHandles\"\nType: array ref\n\nThe ChildHandles attribute contains a reference to an array of all the handles created by this\nhandle which are still accessible. The contents of the array are weak-refs and will become undef\nwhen the handle goes out of scope. (They're cleared out occasionally.)\n\n\"ChildHandles\" returns undef if your perl version does not support weak references (check the\nScalar::Util module). The referenced array returned should be treated as read-only.\n\nFor example, to enumerate all driver handles, database handles and statement handles:\n\nsub showchildhandles {\nmy ($h, $level) = @;\nprintf \"%sh %s %s\\n\", $h->{Type}, \"\\t\" x $level, $h;\nshowchildhandles($, $level + 1)\nfor (grep { defined } @{$h->{ChildHandles}});\n}\n\nmy %drivers = DBI->installeddrivers();\nshowchildhandles($, 0) for (values %drivers);\n\n\"CompatMode\"\nType: boolean, inherited\n\nThe \"CompatMode\" attribute is used by emulation layers (such as Oraperl) to enable compatible\nbehaviour in the underlying driver (e.g., DBD::Oracle) for this handle. Not normally set by\napplication code.\n\nIt also has the effect of disabling the 'quick FETCH' of attribute values from the handles\nattribute cache. So all attribute values are handled by the drivers own FETCH method. This makes\nthem slightly slower but is useful for special-purpose drivers like DBD::Multiplex.\n\n\"InactiveDestroy\"\nType: boolean\n\nThe default value, false, means a handle will be fully destroyed as normal when the last\nreference to it is removed, just as you'd expect.\n\nIf set true then the handle will be treated by the DESTROY as if it was no longer Active, and so\nthe *database engine* related effects of DESTROYing a handle will be skipped. Think of the name\nas meaning 'treat the handle as not-Active in the DESTROY method'.\n\nFor a database handle, this attribute does not disable an *explicit* call to the disconnect\nmethod, only the implicit call from DESTROY that happens if the handle is still marked as\n\"Active\".\n\nThis attribute is specifically designed for use in Unix applications that \"fork\" child\nprocesses. For some drivers, when the child process exits the destruction of inherited handles\ncause the corresponding handles in the parent process to cease working.\n\nEither the parent or the child process, but not both, should set \"InactiveDestroy\" true on all\ntheir shared handles. Alternatively, and preferably, the \"AutoInactiveDestroy\" can be set in the\nparent on connect.\n\nTo help tracing applications using fork the process id is shown in the trace log whenever a DBI\nor handle trace() method is called. The process id also shown for *every* method call if the DBI\ntrace level (not handle trace level) is set high enough to show the trace from the DBI's method\ndispatcher, e.g. >= 9.\n\n\"AutoInactiveDestroy\"\nType: boolean, inherited\n\nThe \"InactiveDestroy\" attribute, described above, needs to be explicitly set in the child\nprocess after a fork(), on every active database and statement handle. This is a problem if the\ncode that performs the fork() is not under your control, perhaps in a third-party module. Use\n\"AutoInactiveDestroy\" to get around this situation.\n\nIf set true, the DESTROY method will check the process id of the handle and, if different from\nthe current process id, it will set the *InactiveDestroy* attribute. It is strongly recommended\nthat \"AutoInactiveDestroy\" is enabled on all new code (it's only not enabled by default to avoid\nbackwards compatibility problems).\n\nThis is the example it's designed to deal with:\n\nmy $dbh = DBI->connect(...);\nsomecodethatforks(); # Perhaps without your knowledge\n# Child process dies, destroying the inherited dbh\n$dbh->do(...); # Breaks because parent $dbh is now broken\n\nThe \"AutoInactiveDestroy\" attribute was added in DBI 1.614.\n\n\"PrintWarn\"\nType: boolean, inherited\n\nThe \"PrintWarn\" attribute controls the printing of warnings recorded by the driver. When set to\na true value (the default) the DBI will check method calls to see if a warning condition has\nbeen set. If so, the DBI will effectively do a \"warn(\"$class $method warning: $DBI::errstr\")\"\nwhere $class is the driver class and $method is the name of the method which failed. E.g.,\n\nDBD::Oracle::db execute warning: ... warning text here ...\n\nIf desired, the warnings can be caught and processed using a $SIG{WARN} handler or modules\nlike CGI::Carp and CGI::ErrorWrap.\n\nSee also \"seterr\" for how warnings are recorded and \"HandleSetErr\" for how to influence it.\n\nFetching the full details of warnings can require an extra round-trip to the database server for\nsome drivers. In which case the driver may opt to only fetch the full details of warnings if the\n\"PrintWarn\" attribute is true. If \"PrintWarn\" is false then these drivers should still indicate\nthe fact that there were warnings by setting the warning string to, for example: \"3 warnings\".\n\n\"PrintError\"\nType: boolean, inherited\n\nThe \"PrintError\" attribute can be used to force errors to generate warnings (using \"warn\") in\naddition to returning error codes in the normal way. When set \"on\", any method which results in\nan error occurring will cause the DBI to effectively do a \"warn(\"$class $method failed:\n$DBI::errstr\")\" where $class is the driver class and $method is the name of the method which\nfailed. E.g.,\n\nDBD::Oracle::db prepare failed: ... error text here ...\n\nBy default, \"DBI->connect\" sets \"PrintError\" \"on\".\n\nIf desired, the warnings can be caught and processed using a $SIG{WARN} handler or modules\nlike CGI::Carp and CGI::ErrorWrap.\n\n\"RaiseWarn\"\nType: boolean, inherited\n\nThe \"RaiseWarn\" attribute can be used to force warnings to raise exceptions rather then simply\nprinting them. It is \"off\" by default. When set \"on\", any method which sets warning condition\nwill cause the DBI to effectively do a \"die(\"$class $method warning: $DBI::errstr\")\", where\n$class is the driver class and $method is the name of the method that sets warning condition.\nE.g.,\n\nDBD::Oracle::db execute warning: ... warning text here ...\n\nIf you turn \"RaiseWarn\" on then you'd normally turn \"PrintWarn\" off. If \"PrintWarn\" is also on,\nthen the \"PrintWarn\" is done first (naturally).\n\nThis attribute was added in DBI 1.643.\n\n\"RaiseError\"\nType: boolean, inherited\n\nThe \"RaiseError\" attribute can be used to force errors to raise exceptions rather than simply\nreturn error codes in the normal way. It is \"off\" by default. When set \"on\", any method which\nresults in an error will cause the DBI to effectively do a \"die(\"$class $method failed:\n$DBI::errstr\")\", where $class is the driver class and $method is the name of the method that\nfailed. E.g.,\n\nDBD::Oracle::db prepare failed: ... error text here ...\n\nIf you turn \"RaiseError\" on then you'd normally turn \"PrintError\" off. If \"PrintError\" is also\non, then the \"PrintError\" is done first (naturally).\n\nTypically \"RaiseError\" is used in conjunction with \"eval\", or a module like Try::Tiny or\nTryCatch, to catch the exception that's been thrown and handle it. For example:\n\nuse Try::Tiny;\n\ntry {\n...\n$sth->execute();\n...\n} catch {\n# $sth->err and $DBI::err will be true if error was from DBI\nwarn $; # print the error (which Try::Tiny puts into $)\n... # do whatever you need to deal with the error\n};\n\nIn the catch block the $DBI::lasth variable can be useful for diagnosis and reporting if you\ncan't be sure which handle triggered the error. For example, $DBI::lasth->{Type} and\n$DBI::lasth->{Statement}.\n\nSee also \"Transactions\".\n\nIf you want to temporarily turn \"RaiseError\" off (inside a library function that is likely to\nfail, for example), the recommended way is like this:\n\n{\nlocal $h->{RaiseError}; # localize and turn off for this block\n...\n}\n\nThe original value will automatically and reliably be restored by Perl, regardless of how the\nblock is exited. The same logic applies to other attributes, including \"PrintError\".\n\n\"HandleError\"\nType: code ref, inherited\n\nThe \"HandleError\" attribute can be used to provide your own alternative behaviour in case of\nerrors. If set to a reference to a subroutine then that subroutine is called when an error is\ndetected (at the same point that \"RaiseError\" and \"PrintError\" are handled). It is called also\nwhen \"RaiseWarn\" is enabled and a warning is detected.\n\nThe subroutine is called with three parameters: the error message string that \"RaiseError\",\n\"RaiseWarn\" or \"PrintError\" would use, the DBI handle being used, and the first value being\nreturned by the method that failed (typically undef).\n\nIf the subroutine returns a false value then the \"RaiseError\", \"RaiseWarn\" and/or \"PrintError\"\nattributes are checked and acted upon as normal.\n\nFor example, to \"die\" with a full stack trace for any error:\n\nuse Carp;\n$h->{HandleError} = sub { confess(shift) };\n\nOr to turn errors into exceptions:\n\nuse Exception; # or your own favourite exception module\n$h->{HandleError} = sub { Exception->new('DBI')->raise($[0]) };\n\nIt is possible to 'stack' multiple HandleError handlers by using closures:\n\nsub yoursubroutine {\nmy $previoushandler = $h->{HandleError};\n$h->{HandleError} = sub {\nreturn 1 if $previoushandler and &$previoushandler(@);\n... your code here ...\n};\n}\n\nUsing a \"my\" inside a subroutine to store the previous \"HandleError\" value is important. See\nperlsub and perlref for more information about *closures*.\n\nIt is possible for \"HandleError\" to alter the error message that will be used by \"RaiseError\",\n\"RaiseWarn\" and \"PrintError\" if it returns false. It can do that by altering the value of $[0].\nThis example appends a stack trace to all errors and, unlike the previous example using\nCarp::confess, this will work \"PrintError\" as well as \"RaiseError\":\n\n$h->{HandleError} = sub { $[0]=Carp::longmess($[0]); 0; };\n\nIt is also possible for \"HandleError\" to hide an error, to a limited degree, by using \"seterr\"\nto reset $DBI::err and $DBI::errstr, and altering the return value of the failed method. For\nexample:\n\n$h->{HandleError} = sub {\nreturn 0 unless $[0] =~ /^\\S+ fetchrowarrayref failed:/;\nreturn 0 unless $[1]->err == 1234; # the error to 'hide'\n$h->seterr(undef,undef); # turn off the error\n$[2] = [ ... ]; # supply alternative return value\nreturn 1;\n};\n\nThis only works for methods which return a single value and is hard to make reliable (avoiding\ninfinite loops, for example) and so isn't recommended for general use! If you find a *good* use\nfor it then please let me know.\n\n\"HandleSetErr\"\nType: code ref, inherited\n\nThe \"HandleSetErr\" attribute can be used to intercept the setting of handle \"err\", \"errstr\", and\n\"state\" values. If set to a reference to a subroutine then that subroutine is called whenever"
},
{
"name": "set_err",
"content": "The subroutine is called with five arguments, the first five that were passed to seterr(): the\nhandle, the \"err\", \"errstr\", and \"state\" values being set, and the method name. These can be\naltered by changing the values in the @ array. The return value affects seterr() behaviour,\nsee \"seterr\" for details.\n\nIt is possible to 'stack' multiple HandleSetErr handlers by using closures. See \"HandleError\"\nfor an example.\n\nThe \"HandleSetErr\" and \"HandleError\" subroutines differ in subtle but significant ways.\nHandleError is only invoked at the point where the DBI is about to return to the application\nwith \"err\" set true. It's not invoked by the failure of a method that's been called by another\nDBI method. HandleSetErr, on the other hand, is called whenever seterr() is called with a\ndefined \"err\" value, even if false. So it's not just for errors, despite the name, but also warn\nand info states. The seterr() method, and thus HandleSetErr, may be called multiple times\nwithin a method and is usually invoked from deep within driver code.\n\nIn theory a driver can use the return value from HandleSetErr via seterr() to decide whether to\ncontinue or not. If seterr() returns an empty list, indicating that the HandleSetErr code has\n'handled' the 'error', the driver could then continue instead of failing (if that's a reasonable\nthing to do). This isn't excepted to be common and any such cases should be clearly marked in\nthe driver documentation and discussed on the dbi-dev mailing list.\n\nThe \"HandleSetErr\" attribute was added in DBI 1.41.\n\n\"ErrCount\"\nType: unsigned integer\n\nThe \"ErrCount\" attribute is incremented whenever the seterr() method records an error. It isn't\nincremented by warnings or information states. It is not reset by the DBI at any time.\n\nThe \"ErrCount\" attribute was added in DBI 1.41. Older drivers may not have been updated to use"
},
{
"name": "set_err",
"content": "\"ShowErrorStatement\"\nType: boolean, inherited\n\nThe \"ShowErrorStatement\" attribute can be used to cause the relevant Statement text to be\nappended to the error messages generated by the \"RaiseError\", \"PrintError\", \"RaiseWarn\" and\n\"PrintWarn\" attributes. Only applies to errors on statement handles plus the prepare(), do(),\nand the various \"select*()\" database handle methods. (The exact format of the appended text is\nsubject to change.)\n\nIf \"$h->{ParamValues}\" returns a hash reference of parameter (placeholder) values then those are\nformatted and appended to the end of the Statement text in the error message.\n\n\"TraceLevel\"\nType: integer, inherited\n\nThe \"TraceLevel\" attribute can be used as an alternative to the \"trace\" method to set the DBI\ntrace level and trace flags for a specific handle. See \"TRACING\" for more details.\n\nThe \"TraceLevel\" attribute is especially useful combined with \"local\" to alter the trace\nsettings for just a single block of code.\n\n\"FetchHashKeyName\"\nType: string, inherited\n\nThe \"FetchHashKeyName\" attribute is used to specify whether the fetchrowhashref() method should\nperform case conversion on the field names used for the hash keys. For historical reasons it\ndefaults to '\"NAME\"' but it is recommended to set it to '\"NAMElc\"' (convert to lower case) or\n'\"NAMEuc\"' (convert to upper case) according to your preference. It can only be set for driver\nand database handles. For statement handles the value is frozen when prepare() is called.\n\n\"ChopBlanks\"\nType: boolean, inherited\n\nThe \"ChopBlanks\" attribute can be used to control the trimming of trailing space characters from\nfixed width character (CHAR) fields. No other field types are affected, even where field values\nhave trailing spaces.\n\nThe default is false (although it is possible that the default may change). Applications that\nneed specific behaviour should set the attribute as needed.\n\nDrivers are not required to support this attribute, but any driver which does not support it\nmust arrange to return \"undef\" as the attribute value.\n\n\"LongReadLen\"\nType: unsigned integer, inherited\n\nThe \"LongReadLen\" attribute may be used to control the maximum length of 'long' type fields\n(LONG, BLOB, CLOB, MEMO, etc.) which the driver will read from the database automatically when\nit fetches each row of data.\n\nThe \"LongReadLen\" attribute only relates to fetching and reading long values; it is not involved\nin inserting or updating them.\n\nA value of 0 means not to automatically fetch any long data. Drivers may return undef or an\nempty string for long fields when \"LongReadLen\" is 0.\n\nThe default is typically 0 (zero) or 80 bytes but may vary between drivers. Applications\nfetching long fields should set this value to slightly larger than the longest long field value\nto be fetched.\n\nSome databases return some long types encoded as pairs of hex digits. For these types,\n\"LongReadLen\" relates to the underlying data length and not the doubled-up length of the encoded\nstring.\n\nChanging the value of \"LongReadLen\" for a statement handle after it has been \"prepare\"'d will\ntypically have no effect, so it's common to set \"LongReadLen\" on the $dbh before calling\n\"prepare\".\n\nFor most drivers the value used here has a direct effect on the memory used by the statement\nhandle while it's active, so don't be too generous. If you can't be sure what value to use you\ncould execute an extra select statement to determine the longest value. For example:\n\n$dbh->{LongReadLen} = $dbh->selectrowarray(qq{\nSELECT MAX(OCTETLENGTH(longcolumnname))\nFROM table WHERE ...\n});\n$sth = $dbh->prepare(qq{\nSELECT longcolumnname, ... FROM table WHERE ...\n});\n\nYou may need to take extra care if the table can be modified between the first select and the\nsecond being executed. You may also need to use a different function if OCTETLENGTH() does not\nwork for long types in your database. For example, for Sybase use DATALENGTH() and for Oracle\nuse LENGTHB().\n\nSee also \"LongTruncOk\" for information on truncation of long types.\n\n\"LongTruncOk\"\nType: boolean, inherited\n\nThe \"LongTruncOk\" attribute may be used to control the effect of fetching a long field value\nwhich has been truncated (typically because it's longer than the value of the \"LongReadLen\"\nattribute).\n\nBy default, \"LongTruncOk\" is false and so fetching a long value that needs to be truncated will\ncause the fetch to fail. (Applications should always be sure to check for errors after a fetch\nloop in case an error, such as a divide by zero or long field truncation, caused the fetch to\nterminate prematurely.)\n\nIf a fetch fails due to a long field truncation when \"LongTruncOk\" is false, many drivers will\nallow you to continue fetching further rows.\n\nSee also \"LongReadLen\".\n\n\"TaintIn\"\nType: boolean, inherited\n\nIf the \"TaintIn\" attribute is set to a true value *and* Perl is running in taint mode (e.g.,\nstarted with the \"-T\" option), then all the arguments to most DBI method calls are checked for\nbeing tainted. *This may change.*\n\nThe attribute defaults to off, even if Perl is in taint mode. See perlsec for more about taint\nmode. If Perl is not running in taint mode, this attribute has no effect.\n\nWhen fetching data that you trust you can turn off the TaintIn attribute, for that statement\nhandle, for the duration of the fetch loop.\n\nThe \"TaintIn\" attribute was added in DBI 1.31.\n\n\"TaintOut\"\nType: boolean, inherited\n\nIf the \"TaintOut\" attribute is set to a true value *and* Perl is running in taint mode (e.g.,\nstarted with the \"-T\" option), then most data fetched from the database is considered tainted.\n*This may change.*\n\nThe attribute defaults to off, even if Perl is in taint mode. See perlsec for more about taint\nmode. If Perl is not running in taint mode, this attribute has no effect.\n\nWhen fetching data that you trust you can turn off the TaintOut attribute, for that statement\nhandle, for the duration of the fetch loop.\n\nCurrently only fetched data is tainted. It is possible that the results of other DBI method\ncalls, and the value of fetched attributes, may also be tainted in future versions. That change\nmay well break your applications unless you take great care now. If you use DBI Taint mode,\nplease report your experience and any suggestions for changes.\n\nThe \"TaintOut\" attribute was added in DBI 1.31.\n\n\"Taint\"\nType: boolean, inherited\n\nThe \"Taint\" attribute is a shortcut for \"TaintIn\" and \"TaintOut\" (it is also present for\nbackwards compatibility).\n\nSetting this attribute sets both \"TaintIn\" and \"TaintOut\", and retrieving it returns a true\nvalue if and only if \"TaintIn\" and \"TaintOut\" are both set to true values.\n\n\"Profile\"\nType: inherited\n\nThe \"Profile\" attribute enables the collection and reporting of method call timing statistics.\nSee the DBI::Profile module documentation for *much* more detail.\n\nThe \"Profile\" attribute was added in DBI 1.24.\n\n\"ReadOnly\"\nType: boolean, inherited\n\nAn application can set the \"ReadOnly\" attribute of a handle to a true value to indicate that it\nwill not be attempting to make any changes using that handle or any children of it.\n\nNote that the exact definition of 'read only' is rather fuzzy. For more details see the\ndocumentation for the driver you're using.\n\nIf the driver can make the handle truly read-only then it should (unless doing so would have\nunpleasant side effect, like changing the consistency level from per-statement to per-session).\nOtherwise the attribute is simply advisory.\n\nA driver can set the \"ReadOnly\" attribute itself to indicate that the data it is connected to\ncannot be changed for some reason.\n\nIf the driver cannot ensure the \"ReadOnly\" attribute is adhered to it will record a warning. In\nthis case reading the \"ReadOnly\" attribute back after it is set true will return true even if\nthe underlying driver cannot ensure this (so any application knows the application declared\nitself ReadOnly).\n\nLibrary modules and proxy drivers can use the attribute to influence their behavior. For\nexample, the DBD::Gofer driver considers the \"ReadOnly\" attribute when making a decision about\nwhether to retry an operation that failed.\n\nThe attribute should be set to 1 or 0 (or undef). Other values are reserved.\n\n\"Callbacks\"\nType: hash ref\n\nThe DBI callback mechanism lets you intercept, and optionally replace, any method call on a DBI\nhandle. At the extreme, it lets you become a puppet master, deceiving the application in any way\nyou want.\n\nThe \"Callbacks\" attribute is a hash reference where the keys are DBI method names and the values\nare code references. For each key naming a method, the DBI will execute the associated code\nreference before executing the method.\n\nThe arguments to the code reference will be the same as to the method, including the invocant (a\ndatabase handle or statement handle). For example, say that to callback to some code on a call\nto \"prepare()\":\n\n$dbh->{Callbacks} = {\nprepare => sub {\nmy ($dbh, $query, $attrs) = @;\nprint \"Preparing q{$query}\\n\"\n},\n};\n\nThe callback would then be executed when you called the \"prepare()\" method:\n\n$dbh->prepare('SELECT 1');\n\nAnd the output of course would be:\n\nPreparing q{SELECT 1}\n\nBecause callbacks are executed *before* the methods they're associated with, you can modify the\narguments before they're passed on to the method call. For example, to make sure that all calls\nto \"prepare()\" are immediately prepared by DBD::Pg, add a callback that makes sure that the\n\"pgpreparenow\" attribute is always set:\n\nmy $dbh = DBI->connect($dsn, $username, $auth, {\nCallbacks => {\nprepare => sub {\n$[2] ||= {};\n$[2]->{pgpreparenow} = 1;\nreturn; # must return nothing\n},\n}\n});\n\nNote that we are editing the contents of @ directly. In this case we've created the attributes\nhash if it's not passed to the \"prepare\" call.\n\nYou can also prevent the associated method from ever executing. While a callback executes, $\nholds the method name. (This allows multiple callbacks to share the same code reference and\nstill know what method was called.) To prevent the method from executing, simply \"undef $\". For\nexample, if you wanted to disable calls to \"ping()\", you could do this:\n\n$dbh->{Callbacks} = {\nping => sub {\n# tell dispatch to not call the method:\nundef $;\n# return this value instead:\nreturn \"42 bells\";\n}\n};\n\nAs with other attributes, Callbacks can be specified on a handle or via the attributes to\n\"connect()\". Callbacks can also be applied to a statement methods on a statement handle. For\nexample:\n\n$sth->{Callbacks} = {\nexecute => sub {\nprint \"Executing \", shift->{Statement}, \"\\n\";\n}\n};\n\nThe \"Callbacks\" attribute of a database handle isn't copied to any statement handles it creates.\nSo setting callbacks for a statement handle requires you to set the \"Callbacks\" attribute on the\nstatement handle yourself, as in the example above, or use the special \"ChildCallbacks\" key\ndescribed below.\n\nSpecial Keys in Callbacks Attribute\n\nIn addition to DBI handle method names, the \"Callbacks\" hash reference supports four additional\nkeys.\n\nThe first is the \"ChildCallbacks\" key. When a statement handle is created from a database handle\nthe \"ChildCallbacks\" key of the database handle's \"Callbacks\" attribute, if any, becomes the new\n\"Callbacks\" attribute of the statement handle. This allows you to define callbacks for all\nstatement handles created from a database handle. For example, if you wanted to count how many\ntimes \"execute\" was called in your application, you could write:\n\nmy $execcount = 0;\nmy $dbh = DBI->connect( $dsn, $username, $auth, {\nCallbacks => {\nChildCallbacks => {\nexecute => sub { $execcount++; return; }\n}\n}\n});\n\nEND {\nprint \"The execute method was called $execcount times\\n\";\n}\n\nThe other three special keys are \"connectcached.new\", \"connectcached.connected\", and\n\"connectcached.reused\". These keys define callbacks that are called when \"connectcached()\" is\ncalled, but allow different behaviors depending on whether a new handle is created or a handle\nis returned. The callback is invoked with these arguments: \"$dbh, $dsn, $user, $auth, $attr\".\n\nFor example, some applications uses \"connectcached()\" to connect with \"AutoCommit\" enabled and\nthen disable \"AutoCommit\" temporarily for transactions. If \"connectcached()\" is called during a\ntransaction, perhaps in a utility method, then it might select the same cached handle and then\nforce \"AutoCommit\" on, forcing a commit of the transaction. See the \"connectcached\"\ndocumentation for one way to deal with that. Here we'll describe an alternative approach using a\ncallback.\n\nBecause the \"connectcached.new\" and \"connectcached.reused\" callbacks are invoked before\n\"connectcached()\" has applied the connect attributes, you can use them to edit the attributes\nthat will be applied. To prevent a cached handle from having its transactions committed before\nit's returned, you can eliminate the \"AutoCommit\" attribute in a \"connectcached.reused\"\ncallback, like so:\n\nmy $cb = {\n'connectcached.reused' => sub { delete $[4]->{AutoCommit} },\n};\n\nsub dbh {\nmy $self = shift;\nDBI->connectcached( $dsn, $username, $auth, {\nPrintError => 0,\nRaiseError => 1,\nAutoCommit => 1,\nCallbacks => $cb,\n});\n}\n\nThe upshot is that new database handles are created with \"AutoCommit\" enabled, while cached\ndatabase handles are left in whatever transaction state they happened to be in when retrieved\nfrom the cache.\n\nNote that we've also used a lexical for the callbacks hash reference. This is because\n\"connectcached()\" returns a new database handle if any of the attributes passed to is have\nchanged. If we used an inline hash reference, \"connectcached()\" would return a new database\nhandle every time. Which would rather defeat the purpose.\n\nA more common application for callbacks is setting connection state only when a new connection\nis made (by connect() or connectcached()). Adding a callback to the connected method (when\nusing \"connect\") or via \"connectcached.connected\" (when useing connectcached()>) makes this\neasy. The connected() method is a no-op by default (unless you subclass the DBI and change it).\nThe DBI calls it to indicate that a new connection has been made and the connection attributes\nhave all been set. You can give it a bit of added functionality by applying a callback to it.\nFor example, to make sure that MySQL understands your application's ANSI-compliant SQL, set it\nup like so:\n\nmy $dbh = DBI->connect($dsn, $username, $auth, {\nCallbacks => {\nconnected => sub {\nshift->do(q{\nSET SESSION sqlmode='ansi,stricttranstables,noautovalueonzero';\n});\nreturn;\n},\n}\n});\n\nIf you're using \"connectcached()\", use the \"connectcached.connected\" callback, instead. This\nis because \"connected()\" is called for both new and reused database handles, but you want to\nexecute a callback only the when a new database handle is returned. For example, to set the time\nzone on connection to a PostgreSQL database, try this:\n\nmy $cb = {\n'connectcached.connected' => sub {\nshift->do('SET timezone = UTC');\n}\n};\n\nsub dbh {\nmy $self = shift;\nDBI->connectcached( $dsn, $username, $auth, { Callbacks => $cb });\n}\n\nOne significant limitation with callbacks is that there can only be one per method per handle.\nThis means it's easy for one use of callbacks to interfere with, or typically simply overwrite,\nanother use of callbacks. For this reason modules using callbacks should document the fact\nclearly so application authors can tell if use of callbacks by the module will clash with use of\ncallbacks by the application.\n\nYou might be able to work around this issue by taking a copy of the original callback and\ncalling it within your own. For example:\n\nmy $prevcb = $h->{Callbacks}{methodname};\n$h->{Callbacks}{methodname} = sub {\nif ($prevcb) {\nmy @result = $prevcb->(@);\nreturn @result if not $; # $prevcb vetoed call\n}\n... your callback logic here ...\n};\n\n\"privateyourmodulename*\"\nThe DBI provides a way to store extra information in a DBI handle as \"private\" attributes. The\nDBI will allow you to store and retrieve any attribute which has a name starting with\n\"\"private\"\".\n\nIt is *strongly* recommended that you use just *one* private attribute (e.g., use a hash ref)\n*and* give it a long and unambiguous name that includes the module or application name that the\nattribute relates to (e.g., \"\"privateYourFullModuleNamethingy\"\").\n\nBecause of the way the Perl tie mechanism works you cannot reliably use the \"||=\" operator\ndirectly to initialise the attribute, like this:\n\nmy $foo = $dbh->{privateyourmodnamefoo} ||= { ... }; # WRONG\n\nyou should use a two step approach like this:\n\nmy $foo = $dbh->{privateyourmodnamefoo};\n$foo ||= $dbh->{privateyourmodnamefoo} = { ... };\n\nThis attribute is primarily of interest to people sub-classing DBI, or for applications to\npiggy-back extra information onto DBI handles.\n"
}
]
},
"DBI DATABASE HANDLE OBJECTS": {
"content": "This section covers the methods and attributes associated with database handles.\n",
"subsections": [
{
"name": "Database Handle Methods",
"content": "The following methods are specified for DBI database handles:\n\n\"clone\"\n$newdbh = $dbh->clone(\\%attr);\n\nThe \"clone\" method duplicates the $dbh connection by connecting with the same parameters ($dsn,\n$user, $password) as originally used.\n\nThe attributes for the cloned connect are the same as those used for the *original* connect,\nwith any other attributes in \"\\%attr\" merged over them. Effectively the same as doing:\n\n%attributesused = ( %originalattributes, %attr );\n\nIf \\%attr is not given then it defaults to a hash containing all the attributes in the attribute\ncache of $dbh excluding any non-code references, plus the main boolean attributes (RaiseError,\nPrintError, AutoCommit, etc.). *This behaviour is unreliable and so use of clone without an\nargument is deprecated and may cause a warning in a future release.*\n\nThe clone method can be used even if the database handle is disconnected.\n\nThe \"clone\" method was added in DBI 1.33.\n\n\"datasources\"\n@ary = $dbh->datasources();\n@ary = $dbh->datasources(\\%attr);\n\nReturns a list of data sources (databases) available via the $dbh driver's datasources()\nmethod, plus any extra data sources that the driver can discover via the connected $dbh.\nTypically the extra data sources are other databases managed by the same server process that the\n$dbh is connected to.\n\nData sources are returned in a form suitable for passing to the \"connect\" method (that is, they\nwill include the \"\"dbi:$driver:\"\" prefix).\n\nThe datasources() method, for a $dbh, was added in DBI 1.38.\n\n\"do\"\n$rows = $dbh->do($statement) or die $dbh->errstr;\n$rows = $dbh->do($statement, \\%attr) or die $dbh->errstr;\n$rows = $dbh->do($statement, \\%attr, @bindvalues) or die ...\n\nPrepare and execute a single statement. Returns the number of rows affected or \"undef\" on error.\nA return value of -1 means the number of rows is not known, not applicable, or not available.\n\nThis method is typically most useful for *non*-\"SELECT\" statements that either cannot be\nprepared in advance (due to a limitation of the driver) or do not need to be executed\nrepeatedly. It should not be used for \"SELECT\" statements because it does not return a statement\nhandle (so you can't fetch any data).\n\nThe default \"do\" method is logically similar to:\n\nsub do {\nmy($dbh, $statement, $attr, @bindvalues) = @;\nmy $sth = $dbh->prepare($statement, $attr) or return undef;\n$sth->execute(@bindvalues) or return undef;\nmy $rows = $sth->rows;\n($rows == 0) ? \"0E0\" : $rows; # always return true if no error\n}\n\nFor example:\n\nmy $rowsdeleted = $dbh->do(q{\nDELETE FROM table\nWHERE status = ?\n}, undef, 'DONE') or die $dbh->errstr;\n\nUsing placeholders and @bindvalues with the \"do\" method can be useful because it avoids the\nneed to correctly quote any variables in the $statement. But if you'll be executing the\nstatement many times then it's more efficient to \"prepare\" it once and call \"execute\" many times\ninstead.\n\nThe \"q{...}\" style quoting used in this example avoids clashing with quotes that may be used in\nthe SQL statement. Use the double-quote-like \"qq{...}\" operator if you want to interpolate\nvariables into the string. See \"Quote and Quote-like Operators\" in perlop for more details.\n\nNote drivers are free to avoid the overhead of creating an DBI statement handle for do(),\nespecially if there are no parameters. In this case error handlers, if invoked during do(), will\nbe passed the database handle.\n\n\"lastinsertid\"\n$rv = $dbh->lastinsertid();\n$rv = $dbh->lastinsertid($catalog, $schema, $table, $field);\n$rv = $dbh->lastinsertid($catalog, $schema, $table, $field, \\%attr);\n\nReturns a value 'identifying' the row just inserted, if possible. Typically this would be a\nvalue assigned by the database server to a column with an *autoincrement* or *serial* type.\nReturns undef if the driver does not support the method or can't determine the value.\n\nThe $catalog, $schema, $table, and $field parameters may be required for some drivers (see\nbelow). If you don't know the parameter values and your driver does not need them, then use\n\"undef\" for each.\n\nThere are several caveats to be aware of with this method if you want to use it for portable\napplications:\n\n* For some drivers the value may only available immediately after the insert statement has\nexecuted (e.g., mysql, Informix).\n\n* For some drivers the $catalog, $schema, $table, and $field parameters are required, for others\nthey are ignored (e.g., mysql).\n\n* Drivers may return an indeterminate value if no insert has been performed yet.\n\n* For some drivers the value may only be available if placeholders have *not* been used (e.g.,\nSybase, MS SQL). In this case the value returned would be from the last non-placeholder insert\nstatement.\n\n* Some drivers may need driver-specific hints about how to get the value. For example, being\ntold the name of the database 'sequence' object that holds the value. Any such hints are passed\nas driver-specific attributes in the \\%attr parameter.\n\n* If the underlying database offers nothing better, then some drivers may attempt to implement\nthis method by executing \"\"select max($field) from $table\"\". Drivers using any approach like\nthis should issue a warning if \"AutoCommit\" is true because it is generally unsafe - another\nprocess may have modified the table between your insert and the select. For situations where you\nknow it is safe, such as when you have locked the table, you can silence the warning by passing\n\"Warn\" => 0 in \\%attr.\n\n* If no insert has been performed yet, or the last insert failed, then the value is\nimplementation defined.\n\nGiven all the caveats above, it's clear that this method must be used with care.\n\nThe \"lastinsertid\" method was added in DBI 1.38.\n\n\"selectrowarray\"\n@rowary = $dbh->selectrowarray($statement);\n@rowary = $dbh->selectrowarray($statement, \\%attr);\n@rowary = $dbh->selectrowarray($statement, \\%attr, @bindvalues);\n\nThis utility method combines \"prepare\", \"execute\" and \"fetchrowarray\" into a single call. If\ncalled in a list context, it returns the first row of data from the statement. The $statement\nparameter can be a previously prepared statement handle, in which case the \"prepare\" is skipped.\n\nIf any method fails, and \"RaiseError\" is not set, \"selectrowarray\" will return an empty list.\n\nIf called in a scalar context for a statement handle that has more than one column, it is\nundefined whether the driver will return the value of the first column or the last. So don't do\nthat. Also, in a scalar context, an \"undef\" is returned if there are no more rows or if an error\noccurred. That \"undef\" can't be distinguished from an \"undef\" returned because the first field\nvalue was NULL. For these reasons you should exercise some caution if you use \"selectrowarray\"\nin a scalar context, or just don't do that.\n\n\"selectrowarrayref\"\n$aryref = $dbh->selectrowarrayref($statement);\n$aryref = $dbh->selectrowarrayref($statement, \\%attr);\n$aryref = $dbh->selectrowarrayref($statement, \\%attr, @bindvalues);\n\nThis utility method combines \"prepare\", \"execute\" and \"fetchrowarrayref\" into a single call. It\nreturns the first row of data from the statement. The $statement parameter can be a previously\nprepared statement handle, in which case the \"prepare\" is skipped.\n\nIf any method fails, and \"RaiseError\" is not set, \"selectrowarrayref\" will return undef.\n\n\"selectrowhashref\"\n$hashref = $dbh->selectrowhashref($statement);\n$hashref = $dbh->selectrowhashref($statement, \\%attr);\n$hashref = $dbh->selectrowhashref($statement, \\%attr, @bindvalues);\n\nThis utility method combines \"prepare\", \"execute\" and \"fetchrowhashref\" into a single call. It\nreturns the first row of data from the statement. The $statement parameter can be a previously\nprepared statement handle, in which case the \"prepare\" is skipped.\n\nIf any method fails, and \"RaiseError\" is not set, \"selectrowhashref\" will return undef.\n\n\"selectallarrayref\"\n$aryref = $dbh->selectallarrayref($statement);\n$aryref = $dbh->selectallarrayref($statement, \\%attr);\n$aryref = $dbh->selectallarrayref($statement, \\%attr, @bindvalues);\n\nThis utility method combines \"prepare\", \"execute\" and \"fetchallarrayref\" into a single call. It\nreturns a reference to an array containing a reference to an array (or hash, see below) for each\nrow of data fetched.\n\nThe $statement parameter can be a previously prepared statement handle, in which case the\n\"prepare\" is skipped. This is recommended if the statement is going to be executed many times.\n\nIf \"RaiseError\" is not set and any method except \"fetchallarrayref\" fails then\n\"selectallarrayref\" will return \"undef\"; if \"fetchallarrayref\" fails then it will return with\nwhatever data has been fetched thus far. You should check \"$dbh->err\" afterwards (or use the\n\"RaiseError\" attribute) to discover if the data is complete or was truncated due to an error.\n\nThe \"fetchallarrayref\" method called by \"selectallarrayref\" supports a $maxrows parameter.\nYou can specify a value for $maxrows by including a '\"MaxRows\"' attribute in \\%attr. In which\ncase finish() is called for you after fetchallarrayref() returns.\n\nThe \"fetchallarrayref\" method called by \"selectallarrayref\" also supports a $slice parameter.\nYou can specify a value for $slice by including a '\"Slice\"' or '\"Columns\"' attribute in \\%attr.\nThe only difference between the two is that if \"Slice\" is not defined and \"Columns\" is an array\nref, then the array is assumed to contain column index values (which count from 1), rather than\nperl array index values. In which case the array is copied and each value decremented before\npassing to \"/fetchallarrayref\".\n\nYou may often want to fetch an array of rows where each row is stored as a hash. That can be\ndone simply using:\n\nmy $emps = $dbh->selectallarrayref(\n\"SELECT ename FROM emp ORDER BY ename\",\n{ Slice => {} }\n);\nforeach my $emp ( @$emps ) {\nprint \"Employee: $emp->{ename}\\n\";\n}\n\nOr, to fetch into an array instead of an array ref:\n\n@result = @{ $dbh->selectallarrayref($sql, { Slice => {} }) };\n\nSee \"fetchallarrayref\" method for more details.\n\n\"selectallarray\"\n@ary = $dbh->selectallarray($statement);\n@ary = $dbh->selectallarray($statement, \\%attr);\n@ary = $dbh->selectallarray($statement, \\%attr, @bindvalues);\n\nThis is a convenience wrapper around selectallarrayref that returns the rows directly as a\nlist, rather than a reference to an array of rows.\n\nNote that if \"RaiseError\" is not set then you can't tell the difference between returning no\nrows and an error. Using RaiseError is best practice.\n\nThe \"selectallarray\" method was added in DBI 1.635.\n\n\"selectallhashref\"\n$hashref = $dbh->selectallhashref($statement, $keyfield);\n$hashref = $dbh->selectallhashref($statement, $keyfield, \\%attr);\n$hashref = $dbh->selectallhashref($statement, $keyfield, \\%attr, @bindvalues);\n\nThis utility method combines \"prepare\", \"execute\" and \"fetchallhashref\" into a single call. It\nreturns a reference to a hash containing one entry, at most, for each row, as returned by"
},
{
"name": "fetchall_hashref",
"content": "The $statement parameter can be a previously prepared statement handle, in which case the\n\"prepare\" is skipped. This is recommended if the statement is going to be executed many times.\n\nThe $keyfield parameter defines which column, or columns, are used as keys in the returned\nhash. It can either be the name of a single field, or a reference to an array containing\nmultiple field names. Using multiple names yields a tree of nested hashes.\n\nIf a row has the same key as an earlier row then it replaces the earlier row.\n\nIf any method except \"fetchallhashref\" fails, and \"RaiseError\" is not set, \"selectallhashref\"\nwill return \"undef\". If \"fetchallhashref\" fails and \"RaiseError\" is not set, then it will\nreturn with whatever data it has fetched thus far. $DBI::err should be checked to catch that.\n\nSee fetchallhashref() for more details.\n\n\"selectcolarrayref\"\n$aryref = $dbh->selectcolarrayref($statement);\n$aryref = $dbh->selectcolarrayref($statement, \\%attr);\n$aryref = $dbh->selectcolarrayref($statement, \\%attr, @bindvalues);\n\nThis utility method combines \"prepare\", \"execute\", and fetching one column from all the rows,\ninto a single call. It returns a reference to an array containing the values of the first column\nfrom each row.\n\nThe $statement parameter can be a previously prepared statement handle, in which case the\n\"prepare\" is skipped. This is recommended if the statement is going to be executed many times.\n\nIf any method except \"fetch\" fails, and \"RaiseError\" is not set, \"selectcolarrayref\" will\nreturn \"undef\". If \"fetch\" fails and \"RaiseError\" is not set, then it will return with whatever\ndata it has fetched thus far. $DBI::err should be checked to catch that.\n\nThe \"selectcolarrayref\" method defaults to pushing a single column value (the first) from each\nrow into the result array. However, it can also push another column, or even multiple columns\nper row, into the result array. This behaviour can be specified via a '\"Columns\"' attribute\nwhich must be a ref to an array containing the column number or numbers to use. For example:\n\n# get array of id and name pairs:\nmy $aryref = $dbh->selectcolarrayref(\"select id, name from table\", { Columns=>[1,2] });\nmy %hash = @$aryref; # build hash from key-value pairs so $hash{$id} => name\n\nYou can specify a maximum number of rows to fetch by including a '\"MaxRows\"' attribute in\n\\%attr.\n\n\"prepare\"\n$sth = $dbh->prepare($statement) or die $dbh->errstr;\n$sth = $dbh->prepare($statement, \\%attr) or die $dbh->errstr;\n\nPrepares a statement for later execution by the database engine and returns a reference to a\nstatement handle object.\n\nThe returned statement handle can be used to get attributes of the statement and invoke the\n\"execute\" method. See \"Statement Handle Methods\".\n\nDrivers for engines without the concept of preparing a statement will typically just store the\nstatement in the returned handle and process it when \"$sth->execute\" is called. Such drivers are\nunlikely to give much useful information about the statement, such as \"$sth->{NUMOFFIELDS}\",\nuntil after \"$sth->execute\" has been called. Portable applications should take this into\naccount.\n\nIn general, DBI drivers do not parse the contents of the statement (other than simply counting\nany Placeholders). The statement is passed directly to the database engine, sometimes known as\npass-thru mode. This has advantages and disadvantages. On the plus side, you can access all the\nfunctionality of the engine being used. On the downside, you're limited if you're using a simple\nengine, and you need to take extra care if writing applications intended to be portable between\nengines.\n\nPortable applications should not assume that a new statement can be prepared and/or executed\nwhile still fetching results from a previous statement.\n\nSome command-line SQL tools use statement terminators, like a semicolon, to indicate the end of\na statement. Such terminators should not normally be used with the DBI.\n\n\"preparecached\"\n$sth = $dbh->preparecached($statement)\n$sth = $dbh->preparecached($statement, \\%attr)\n$sth = $dbh->preparecached($statement, \\%attr, $ifactive)\n\nLike \"prepare\" except that the statement handle returned will be stored in a hash associated\nwith the $dbh. If another call is made to \"preparecached\" with the same $statement and %attr\nparameter values, then the corresponding cached $sth will be returned without contacting the\ndatabase server. Be sure to understand the cautions and caveats noted below.\n\nThe $ifactive parameter lets you adjust the behaviour if an already cached statement handle is\nstill Active. There are several alternatives:\n\n0: A warning will be generated, and finish() will be called on the statement handle before it is\nreturned. This is the default behaviour if $ifactive is not passed.\n1: finish() will be called on the statement handle, but the warning is suppressed.\n2: Disables any checking.\n3: The existing active statement handle will be removed from the cache and a new statement\nhandle prepared and cached in its place. This is the safest option because it doesn't affect the\nstate of the old handle, it just removes it from the cache. [Added in DBI 1.40]\n\nHere are some examples of \"preparecached\":\n\nsub inserthash {\nmy ($table, $fieldvalues) = @;\n# sort to keep field order, and thus sql, stable for preparecached\nmy @fields = sort keys %$fieldvalues;\nmy @values = @{$fieldvalues}{@fields};\nmy $sql = sprintf \"insert into %s (%s) values (%s)\",\n$table, join(\",\", @fields), join(\",\", (\"?\")x@fields);\nmy $sth = $dbh->preparecached($sql);\nreturn $sth->execute(@values);\n}\n\nsub searchhash {\nmy ($table, $fieldvalues) = @;\n# sort to keep field order, and thus sql, stable for preparecached\nmy @fields = sort keys %$fieldvalues;\nmy @values = @{$fieldvalues}{@fields};\nmy $qualifier = \"\";\n$qualifier = \"where \".join(\" and \", map { \"$=?\" } @fields) if @fields;\n$sth = $dbh->preparecached(\"SELECT * FROM $table $qualifier\");\nreturn $dbh->selectallarrayref($sth, {}, @values);\n}\n\n*Caveat emptor:* This caching can be useful in some applications, but it can also cause problems\nand should be used with care. Here is a contrived case where caching would cause a significant\nproblem:\n\nmy $sth = $dbh->preparecached('SELECT * FROM foo WHERE bar=?');\n$sth->execute(...);\nwhile (my $data = $sth->fetchrowhashref) {\n\n# later, in some other code called within the loop...\nmy $sth2 = $dbh->preparecached('SELECT * FROM foo WHERE bar=?');\n$sth2->execute(...);\nwhile (my $data2 = $sth2->fetchrowarrayref) {\ndostuff(...);\n}\n}\n\nIn this example, since both handles are preparing the exact same statement, $sth2 will not be\nits own statement handle, but a duplicate of $sth returned from the cache. The results will\ncertainly not be what you expect. Typically the inner fetch loop will work normally, fetching\nall the records and terminating when there are no more, but now that $sth is the same as $sth2\nthe outer fetch loop will also terminate.\n\nYou'll know if you run into this problem because preparecached() will generate a warning by\ndefault (when $ifactive is false).\n\nThe cache used by preparecached() is keyed by both the statement and any attributes so you can\nalso avoid this issue by doing something like:\n\n$sth = $dbh->preparecached(\"...\", { dbidummy => FILE.LINE });\n\nwhich will ensure that preparecached only returns statements cached by that line of code in\nthat source file.\n\nAlso, to ensure the attributes passed are always the same, avoid passing references inline. For\nexample, the Slice attribute is specified as a reference. Be sure to declare it external to the\ncall to preparecached(), such that a new hash reference is not created on every call. See\n\"connectcached\" for more details and examples.\n\nIf you'd like the cache to managed intelligently, you can tie the hashref returned by\n\"CachedKids\" to an appropriate caching module, such as Tie::Cache::LRU:\n\nmy $cache;\ntie %$cache, 'Tie::Cache::LRU', 500;\n$dbh->{CachedKids} = $cache;\n\n\"commit\"\n$rc = $dbh->commit or die $dbh->errstr;\n\nCommit (make permanent) the most recent series of database changes if the database supports\ntransactions and AutoCommit is off.\n\nIf \"AutoCommit\" is on, then calling \"commit\" will issue a \"commit ineffective with AutoCommit\"\nwarning.\n\nSee also \"Transactions\" in the \"FURTHER INFORMATION\" section below.\n\n\"rollback\"\n$rc = $dbh->rollback or die $dbh->errstr;\n\nRollback (undo) the most recent series of uncommitted database changes if the database supports\ntransactions and AutoCommit is off.\n\nIf \"AutoCommit\" is on, then calling \"rollback\" will issue a \"rollback ineffective with\nAutoCommit\" warning.\n\nSee also \"Transactions\" in the \"FURTHER INFORMATION\" section below.\n\n\"beginwork\"\n$rc = $dbh->beginwork or die $dbh->errstr;\n\nEnable transactions (by turning \"AutoCommit\" off) until the next call to \"commit\" or \"rollback\".\nAfter the next \"commit\" or \"rollback\", \"AutoCommit\" will automatically be turned on again.\n\nIf \"AutoCommit\" is already off when \"beginwork\" is called then it does nothing except return an\nerror. If the driver does not support transactions then when \"beginwork\" attempts to set\n\"AutoCommit\" off the driver will trigger a fatal error.\n\nSee also \"Transactions\" in the \"FURTHER INFORMATION\" section below.\n\n\"disconnect\"\n$rc = $dbh->disconnect or warn $dbh->errstr;\n\nDisconnects the database from the database handle. \"disconnect\" is typically only used before\nexiting the program. The handle is of little use after disconnecting.\n\nThe transaction behaviour of the \"disconnect\" method is, sadly, undefined. Some database systems\n(such as Oracle and Ingres) will automatically commit any outstanding changes, but others (such\nas Informix) will rollback any outstanding changes. Applications not using \"AutoCommit\" should\nexplicitly call \"commit\" or \"rollback\" before calling \"disconnect\".\n\nThe database is automatically disconnected by the \"DESTROY\" method if still connected when there\nare no longer any references to the handle. The \"DESTROY\" method for each driver should\nimplicitly call \"rollback\" to undo any uncommitted changes. This is vital behaviour to ensure\nthat incomplete transactions don't get committed simply because Perl calls \"DESTROY\" on every\nobject before exiting. Also, do not rely on the order of object destruction during \"global\ndestruction\", as it is undefined.\n\nGenerally, if you want your changes to be committed or rolled back when you disconnect, then you\nshould explicitly call \"commit\" or \"rollback\" before disconnecting.\n\nIf you disconnect from a database while you still have active statement handles (e.g., SELECT\nstatement handles that may have more data to fetch), you will get a warning. The warning may\nindicate that a fetch loop terminated early, perhaps due to an uncaught error. To avoid the\nwarning call the \"finish\" method on the active handles.\n\n\"ping\"\n$rc = $dbh->ping;\n\nAttempts to determine, in a reasonably efficient way, if the database server is still running\nand the connection to it is still working. Individual drivers should implement this function in\nthe most suitable manner for their database engine.\n\nThe current *default* implementation always returns true without actually doing anything.\nActually, it returns \"\"0 but true\"\" which is true but zero. That way you can tell if the return\nvalue is genuine or just the default. Drivers should override this method with one that does the\nright thing for their type of database.\n\nFew applications would have direct use for this method. See the specialized Apache::DBI module\nfor one example usage.\n\n\"getinfo\"\n$value = $dbh->getinfo( $infotype );\n\nReturns information about the implementation, i.e. driver and data source capabilities,\nrestrictions etc. It returns \"undef\" for unknown or unimplemented information types. For\nexample:\n\n$databaseversion = $dbh->getinfo( 18 ); # SQLDBMSVER\n$maxselecttables = $dbh->getinfo( 106 ); # SQLMAXIMUMTABLESINSELECT\n\nSee \"Standards Reference Information\" for more detailed information about the information types\nand their meanings and possible return values.\n\nThe DBI::Const::GetInfoType module exports a %GetInfoType hash that can be used to map info type\nnames to numbers. For example:\n\n$databaseversion = $dbh->getinfo( $GetInfoType{SQLDBMSVER} );\n\nThe names are a merging of the ANSI and ODBC standards (which differ in some cases). See\nDBI::Const::GetInfoType for more details.\n\nBecause some DBI methods make use of getinfo(), drivers are strongly encouraged to support *at\nleast* the following very minimal set of information types to ensure the DBI itself works\nproperly:\n\nType Name Example A Example B\n---- -------------------------- ------------ ----------------\n17 SQLDBMSNAME 'ACCESS' 'Oracle'\n18 SQLDBMSVER '03.50.0000' '08.01.0721 ...'\n29 SQLIDENTIFIERQUOTECHAR '`' '\"'\n41 SQLCATALOGNAMESEPARATOR '.' '@'\n114 SQLCATALOGLOCATION 1 2\n\nValues from 9000 to 9999 for getinfo are officially reserved for use by Perl DBI. Values in\nthat range which have been assigned a meaning are defined here:\n\n9000: true if a backslash character (\"\\\") before placeholder-like text (e.g. \"?\", \":foo\") will\nprevent it being treated as a placeholder by the driver. The backslash will be removed before\nthe text is passed to the backend.\n\n\"tableinfo\"\n$sth = $dbh->tableinfo( $catalog, $schema, $table, $type );\n$sth = $dbh->tableinfo( $catalog, $schema, $table, $type, \\%attr );\n\n# then $sth->fetchallarrayref or $sth->fetchallhashref etc\n\nReturns an active statement handle that can be used to fetch information about tables and views\nthat exist in the database.\n\nThe arguments $catalog, $schema and $table may accept search patterns according to the\ndatabase/driver, for example: $table = '%FOO%'; Remember that the underscore character ('\"\"')\nis a search pattern that means match any character, so 'FOO%' is the same as 'FOO%' and\n'FOOBAR%' will match names like 'FOO1BAR'.\n\nThe value of $type is a comma-separated list of one or more types of tables to be returned in\nthe result set. Each value may optionally be quoted, e.g.:\n\n$type = \"TABLE\";\n$type = \"'TABLE','VIEW'\";\n\nIn addition the following special cases may also be supported by some drivers:\n\n* If the value of $catalog is '%' and $schema and $table name are empty strings, the result\nset contains a list of catalog names. For example:\n\n$sth = $dbh->tableinfo('%', '', '');\n\n* If the value of $schema is '%' and $catalog and $table are empty strings, the result set\ncontains a list of schema names.\n\n* If the value of $type is '%' and $catalog, $schema, and $table are all empty strings, the\nresult set contains a list of table types.\n\nIf your driver doesn't support one or more of the selection filter parameters then you may get\nback more than you asked for and can do the filtering yourself.\n\nThis method can be expensive, and can return a large amount of data. (For example, small Oracle\ninstallation returns over 2000 rows.) So it's a good idea to use the filters to limit the data\nas much as possible.\n\nThe statement handle returned has at least the following fields in the order show below. Other\nfields, after these, may also be present.\n\nTABLECAT: Table catalog identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, which is usually the case. This field is empty if not applicable to the table.\n\nTABLESCHEM: The name of the schema containing the TABLENAME value. This field is NULL\n(\"undef\") if not applicable to data source, and empty if not applicable to the table.\n\nTABLENAME: Name of the table (or view, synonym, etc).\n\nTABLETYPE: One of the following: \"TABLE\", \"VIEW\", \"SYSTEM TABLE\", \"GLOBAL TEMPORARY\", \"LOCAL\nTEMPORARY\", \"ALIAS\", \"SYNONYM\" or a type identifier that is specific to the data source.\n\nREMARKS: A description of the table. May be NULL (\"undef\").\n\nNote that \"tableinfo\" might not return records for all tables. Applications can use any valid\ntable regardless of whether it's returned by \"tableinfo\".\n\nSee also \"tables\", \"Catalog Methods\" and \"Standards Reference Information\".\n\n\"columninfo\"\n$sth = $dbh->columninfo( $catalog, $schema, $table, $column );\n\n# then $sth->fetchallarrayref or $sth->fetchallhashref etc\n\nReturns an active statement handle that can be used to fetch information about columns in\nspecified tables.\n\nThe arguments $schema, $table and $column may accept search patterns according to the\ndatabase/driver, for example: $table = '%FOO%';\n\nNote: The support for the selection criteria is driver specific. If the driver doesn't support\none or more of them then you may get back more than you asked for and can do the filtering\nyourself.\n\nNote: If your driver does not support columninfo an undef is returned. This is distinct from\nasking for something which does not exist in a driver which supports columninfo as a valid\nstatement handle to an empty result-set will be returned in this case.\n\nIf the arguments don't match any tables then you'll still get a statement handle, it'll just\nreturn no rows.\n\nThe statement handle returned has at least the following fields in the order shown below. Other\nfields, after these, may also be present.\n\nTABLECAT: The catalog identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, which is often the case. This field is empty if not applicable to the table.\n\nTABLESCHEM: The schema identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, and empty if not applicable to the table.\n\nTABLENAME: The table identifier. Note: A driver may provide column metadata not only for base\ntables, but also for derived objects like SYNONYMS etc.\n\nCOLUMNNAME: The column identifier.\n\nDATATYPE: The concise data type code.\n\nTYPENAME: A data source dependent data type name.\n\nCOLUMNSIZE: The column size. This is the maximum length in characters for character data types,\nthe number of digits or bits for numeric data types or the length in the representation of\ntemporal types. See the relevant specifications for detailed information.\n\nBUFFERLENGTH: The length in bytes of transferred data.\n\nDECIMALDIGITS: The total number of significant digits to the right of the decimal point.\n\nNUMPRECRADIX: The radix for numeric precision. The value is 10 or 2 for numeric data types and\nNULL (\"undef\") if not applicable.\n\nNULLABLE: Indicates if a column can accept NULLs. The following values are defined:\n\nSQLNONULLS 0\nSQLNULLABLE 1\nSQLNULLABLEUNKNOWN 2\n\nREMARKS: A description of the column.\n\nCOLUMNDEF: The default value of the column, in a format that can be used directly in an SQL\nstatement.\n\nNote that this may be an expression and not simply the text used for the default value in the\noriginal CREATE TABLE statement. For example, given:\n\ncol1 char(30) default currentuser -- a 'function'\ncol2 char(30) default 'string' -- a string literal\n\nwhere \"currentuser\" is the name of a function, the corresponding \"COLUMNDEF\" values would be:\n\nDatabase col1 col2\n-------- ---- ----\nOracle: currentuser 'string'\nPostgres: \"currentuser\"() 'string'::text\nMS SQL: (username()) ('string')\n\nSQLDATATYPE: The SQL data type.\n\nSQLDATETIMESUB: The subtype code for datetime and interval data types.\n\nCHAROCTETLENGTH: The maximum length in bytes of a character or binary data type column.\n\nORDINALPOSITION: The column sequence number (starting with 1).\n\nISNULLABLE: Indicates if the column can accept NULLs. Possible values are: 'NO', 'YES' and ''.\n\nSQL/CLI defines the following additional columns:\n\nCHARSETCAT\nCHARSETSCHEM\nCHARSETNAME\nCOLLATIONCAT\nCOLLATIONSCHEM\nCOLLATIONNAME\nUDTCAT\nUDTSCHEM\nUDTNAME\nDOMAINCAT\nDOMAINSCHEM\nDOMAINNAME\nSCOPECAT\nSCOPESCHEM\nSCOPENAME\nMAXCARDINALITY\nDTDIDENTIFIER\nISSELFREF\n\nDrivers capable of supplying any of those values should do so in the corresponding column and\nsupply undef values for the others.\n\nDrivers wishing to provide extra database/driver specific information should do so in extra\ncolumns beyond all those listed above, and use lowercase field names with the driver-specific\nprefix (i.e., 'ora...'). Applications accessing such fields should do so by name and not by\ncolumn number.\n\nThe result set is ordered by TABLECAT, TABLESCHEM, TABLENAME and ORDINALPOSITION.\n\nNote: There is some overlap with statement handle attributes (in perl) and SQLDescribeCol (in\nODBC). However, SQLColumns provides more metadata.\n\nSee also \"Catalog Methods\" and \"Standards Reference Information\".\n\n\"primarykeyinfo\"\n$sth = $dbh->primarykeyinfo( $catalog, $schema, $table );\n\n# then $sth->fetchallarrayref or $sth->fetchallhashref etc\n\nReturns an active statement handle that can be used to fetch information about columns that make\nup the primary key for a table. The arguments don't accept search patterns (unlike"
},
{
"name": "table_info",
"content": "The statement handle will return one row per column, ordered by TABLECAT, TABLESCHEM,\nTABLENAME, and KEYSEQ. If there is no primary key then the statement handle will fetch no\nrows.\n\nNote: The support for the selection criteria, such as $catalog, is driver specific. If the\ndriver doesn't support catalogs and/or schemas, it may ignore these criteria.\n\nThe statement handle returned has at least the following fields in the order shown below. Other\nfields, after these, may also be present.\n\nTABLECAT: The catalog identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, which is often the case. This field is empty if not applicable to the table.\n\nTABLESCHEM: The schema identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, and empty if not applicable to the table.\n\nTABLENAME: The table identifier.\n\nCOLUMNNAME: The column identifier.\n\nKEYSEQ: The column sequence number (starting with 1). Note: This field is named\nORDINALPOSITION in SQL/CLI.\n\nPKNAME: The primary key constraint identifier. This field is NULL (\"undef\") if not applicable\nto the data source.\n\nSee also \"Catalog Methods\" and \"Standards Reference Information\".\n\n\"primarykey\"\n@keycolumnnames = $dbh->primarykey( $catalog, $schema, $table );\n\nSimple interface to the primarykeyinfo() method. Returns a list of the column names that\ncomprise the primary key of the specified table. The list is in primary key column sequence\norder. If there is no primary key then an empty list is returned.\n\n\"foreignkeyinfo\"\n$sth = $dbh->foreignkeyinfo( $pkcatalog, $pkschema, $pktable\n, $fkcatalog, $fkschema, $fktable );\n\n$sth = $dbh->foreignkeyinfo( $pkcatalog, $pkschema, $pktable\n, $fkcatalog, $fkschema, $fktable\n, \\%attr );\n\n# then $sth->fetchallarrayref or $sth->fetchallhashref etc\n\nReturns an active statement handle that can be used to fetch information about foreign keys in\nand/or referencing the specified table(s). The arguments don't accept search patterns (unlike"
},
{
"name": "table_info",
"content": "$pkcatalog, $pkschema, $pktable identify the primary (unique) key table (PKT).\n\n$fkcatalog, $fkschema, $fktable identify the foreign key table (FKT).\n\nIf both PKT and FKT are given, the function returns the foreign key, if any, in table FKT that\nrefers to the primary (unique) key of table PKT. (Note: In SQL/CLI, the result is\nimplementation-defined.)\n\nIf only PKT is given, then the result set contains the primary key of that table and all foreign\nkeys that refer to it.\n\nIf only FKT is given, then the result set contains all foreign keys in that table and the\nprimary keys to which they refer. (Note: In SQL/CLI, the result includes unique keys too.)\n\nFor example:\n\n$sth = $dbh->foreignkeyinfo( undef, $user, 'master');\n$sth = $dbh->foreignkeyinfo( undef, undef, undef , undef, $user, 'detail');\n$sth = $dbh->foreignkeyinfo( undef, $user, 'master', undef, $user, 'detail');\n\n# then $sth->fetchallarrayref or $sth->fetchallhashref etc\n\nNote: The support for the selection criteria, such as $catalog, is driver specific. If the\ndriver doesn't support catalogs and/or schemas, it may ignore these criteria.\n\nThe statement handle returned has the following fields in the order shown below. Because ODBC\nnever includes unique keys, they define different columns in the result set than SQL/CLI.\nSQL/CLI column names are shown in parentheses.\n\nPKTABLECAT ( UKTABLECAT ): The primary (unique) key table catalog identifier. This field is\nNULL (\"undef\") if not applicable to the data source, which is often the case. This field is\nempty if not applicable to the table.\n\nPKTABLESCHEM ( UKTABLESCHEM ): The primary (unique) key table schema identifier. This field\nis NULL (\"undef\") if not applicable to the data source, and empty if not applicable to the\ntable.\n\nPKTABLENAME ( UKTABLENAME ): The primary (unique) key table identifier.\n\nPKCOLUMNNAME (UKCOLUMNNAME ): The primary (unique) key column identifier.\n\nFKTABLECAT ( FKTABLECAT ): The foreign key table catalog identifier. This field is NULL\n(\"undef\") if not applicable to the data source, which is often the case. This field is empty if\nnot applicable to the table.\n\nFKTABLESCHEM ( FKTABLESCHEM ): The foreign key table schema identifier. This field is NULL\n(\"undef\") if not applicable to the data source, and empty if not applicable to the table.\n\nFKTABLENAME ( FKTABLENAME ): The foreign key table identifier.\n\nFKCOLUMNNAME ( FKCOLUMNNAME ): The foreign key column identifier.\n\nKEYSEQ ( ORDINALPOSITION ): The column sequence number (starting with 1).\n\nUPDATERULE ( UPDATERULE ): The referential action for the UPDATE rule. The following codes are\ndefined:\n\nCASCADE 0\nRESTRICT 1\nSET NULL 2\nNO ACTION 3\nSET DEFAULT 4\n\nDELETERULE ( DELETERULE ): The referential action for the DELETE rule. The codes are the same\nas for UPDATERULE.\n\nFKNAME ( FKNAME ): The foreign key name.\n\nPKNAME ( UKNAME ): The primary (unique) key name.\n\nDEFERRABILITY ( DEFERABILITY ): The deferrability of the foreign key constraint. The following\ncodes are defined:\n\nINITIALLY DEFERRED 5\nINITIALLY IMMEDIATE 6\nNOT DEFERRABLE 7\n\n( UNIQUEORPRIMARY ): This column is necessary if a driver includes all candidate (i.e.\nprimary and alternate) keys in the result set (as specified by SQL/CLI). The value of this\ncolumn is UNIQUE if the foreign key references an alternate key and PRIMARY if the foreign key\nreferences a primary key, or it may be undefined if the driver doesn't have access to the\ninformation.\n\nSee also \"Catalog Methods\" and \"Standards Reference Information\".\n\n\"statisticsinfo\"\nWarning: This method is experimental and may change.\n\n$sth = $dbh->statisticsinfo( $catalog, $schema, $table, $uniqueonly, $quick );\n\n# then $sth->fetchallarrayref or $sth->fetchallhashref etc\n\nReturns an active statement handle that can be used to fetch statistical information about a\ntable and its indexes.\n\nThe arguments don't accept search patterns (unlike \"tableinfo\").\n\nIf the boolean argument $uniqueonly is true, only UNIQUE indexes will be returned in the result\nset, otherwise all indexes will be returned.\n\nIf the boolean argument $quick is set, the actual statistical information columns (CARDINALITY\nand PAGES) will only be returned if they are readily available from the server, and might not be\ncurrent. Some databases may return stale statistics or no statistics at all with this flag set.\n\nThe statement handle will return at most one row per column name per index, plus at most one row\nfor the entire table itself, ordered by NONUNIQUE, TYPE, INDEXQUALIFIER, INDEXNAME, and\nORDINALPOSITION.\n\nNote: The support for the selection criteria, such as $catalog, is driver specific. If the\ndriver doesn't support catalogs and/or schemas, it may ignore these criteria.\n\nThe statement handle returned has at least the following fields in the order shown below. Other\nfields, after these, may also be present.\n\nTABLECAT: The catalog identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, which is often the case. This field is empty if not applicable to the table.\n\nTABLESCHEM: The schema identifier. This field is NULL (\"undef\") if not applicable to the data\nsource, and empty if not applicable to the table.\n\nTABLENAME: The table identifier.\n\nNONUNIQUE: Unique index indicator. Returns 0 for unique indexes, 1 for non-unique indexes\n\nINDEXQUALIFIER: Index qualifier identifier. The identifier that is used to qualify the index\nname when doing a \"DROP INDEX\"; NULL (\"undef\") is returned if an index qualifier is not\nsupported by the data source. If a non-NULL (defined) value is returned in this column, it must\nbe used to qualify the index name on a \"DROP INDEX\" statement; otherwise, the TABLESCHEM should\nbe used to qualify the index name.\n\nINDEXNAME: The index identifier.\n\nTYPE: The type of information being returned. Can be any of the following values: 'table',\n'btree', 'clustered', 'content', 'hashed', or 'other'.\n\nIn the case that this field is 'table', all fields other than TABLECAT, TABLESCHEM,\nTABLENAME, TYPE, CARDINALITY, and PAGES will be NULL (\"undef\").\n\nORDINALPOSITION: Column sequence number (starting with 1).\n\nCOLUMNNAME: The column identifier.\n\nASCORDESC: Column sort sequence. \"A\" for Ascending, \"D\" for Descending, or NULL (\"undef\") if\nnot supported for this index.\n\nCARDINALITY: Cardinality of the table or index. For indexes, this is the number of unique values\nin the index. For tables, this is the number of rows in the table. If not supported, the value\nwill be NULL (\"undef\").\n\nPAGES: Number of storage pages used by this table or index. If not supported, the value will be\nNULL (\"undef\").\n\nFILTERCONDITION: The index filter condition as a string. If the index is not a filtered index,\nor it cannot be determined whether the index is a filtered index, this value is NULL (\"undef\").\nIf the index is a filtered index, but the filter condition cannot be determined, this value is\nthe empty string ''. Otherwise it will be the literal filter condition as a string, such as\n\"SALARY <= 4500\".\n\nSee also \"Catalog Methods\" and \"Standards Reference Information\".\n\n\"tables\"\n@names = $dbh->tables( $catalog, $schema, $table, $type );\n@names = $dbh->tables; # deprecated\n\nSimple interface to tableinfo(). Returns a list of matching table names, possibly including a\ncatalog/schema prefix.\n\nSee \"tableinfo\" for a description of the parameters.\n\nIf \"$dbh->getinfo(29)\" returns true (29 is SQLIDENTIFIERQUOTECHAR) then the table names are\nconstructed and quoted by \"quoteidentifier\" to ensure they are usable even if they contain\nwhitespace or reserved words etc. This means that the table names returned will include quote\ncharacters.\n\n\"typeinfoall\"\n$typeinfoall = $dbh->typeinfoall;\n\nReturns a reference to an array which holds information about each data type variant supported\nby the database and driver. The array and its contents should be treated as read-only.\n\nThe first item is a reference to an 'index' hash of \"Name =\"> \"Index\" pairs. The items following\nthat are references to arrays, one per supported data type variant. The leading index hash\ndefines the names and order of the fields within the arrays that follow it. For example:\n\n$typeinfoall = [\n{ TYPENAME => 0,\nDATATYPE => 1,\nCOLUMNSIZE => 2, # was PRECISION originally\nLITERALPREFIX => 3,\nLITERALSUFFIX => 4,\nCREATEPARAMS => 5,\nNULLABLE => 6,\nCASESENSITIVE => 7,\nSEARCHABLE => 8,\nUNSIGNEDATTRIBUTE=> 9,\nFIXEDPRECSCALE => 10, # was MONEY originally\nAUTOUNIQUEVALUE => 11, # was AUTOINCREMENT originally\nLOCALTYPENAME => 12,\nMINIMUMSCALE => 13,\nMAXIMUMSCALE => 14,\nSQLDATATYPE => 15,\nSQLDATETIMESUB => 16,\nNUMPRECRADIX => 17,\nINTERVALPRECISION=> 18,\n},\n[ 'VARCHAR', SQLVARCHAR,\nundef, \"'\",\"'\", undef,0, 1,1,0,0,0,undef,1,255, undef\n],\n[ 'INTEGER', SQLINTEGER,\nundef, \"\", \"\", undef,0, 0,1,0,0,0,undef,0, 0, 10\n],\n];\n\nMore than one row may have the same value in the \"DATATYPE\" field if there are different ways\nto spell the type name and/or there are variants of the type with different attributes (e.g.,\nwith and without \"AUTOUNIQUEVALUE\" set, with and without \"UNSIGNEDATTRIBUTE\", etc).\n\nThe rows are ordered by \"DATATYPE\" first and then by how closely each type maps to the\ncorresponding ODBC SQL data type, closest first.\n\nThe meaning of the fields is described in the documentation for the \"typeinfo\" method.\n\nAn 'index' hash is provided so you don't need to rely on index values defined above. However,\nusing DBD::ODBC with some old ODBC drivers may return older names, shown as comments in the\nexample above. Another issue with the index hash is that the lettercase of the keys is not\ndefined. It is usually uppercase, as show here, but drivers may return names with any\nlettercase.\n\nDrivers are also free to return extra driver-specific columns of information - though it's\nrecommended that they start at column index 50 to leave room for expansion of the DBI/ODBC\nspecification.\n\nThe typeinfoall() method is not normally used directly. The \"typeinfo\" method provides a more\nusable and useful interface to the data.\n\n\"typeinfo\"\n@typeinfo = $dbh->typeinfo($datatype);\n\nReturns a list of hash references holding information about one or more variants of $datatype.\nThe list is ordered by \"DATATYPE\" first and then by how closely each type maps to the\ncorresponding ODBC SQL data type, closest first. If called in a scalar context then only the\nfirst (best) element is returned.\n\nIf $datatype is undefined or \"SQLALLTYPES\", then the list will contain hashes for all data\ntype variants supported by the database and driver.\n\nIf $datatype is an array reference then \"typeinfo\" returns the information for the *first*\ntype in the array that has any matches.\n\nThe keys of the hash follow the same letter case conventions as the rest of the DBI (see \"Naming\nConventions and Name Space\"). The following uppercase items should always exist, though may be\nundef:\n\nTYPENAME (string)\nData type name for use in CREATE TABLE statements etc.\n\nDATATYPE (integer)\nSQL data type number.\n\nCOLUMNSIZE (integer)\nFor numeric types, this is either the total number of digits (if the NUMPRECRADIX value is\n10) or the total number of bits allowed in the column (if NUMPRECRADIX is 2).\n\nFor string types, this is the maximum size of the string in characters.\n\nFor date and interval types, this is the maximum number of characters needed to display the\nvalue.\n\nLITERALPREFIX (string)\nCharacters used to prefix a literal. A typical prefix is \"\"'\"\" for characters, or possibly\n\"\"0x\"\" for binary values passed as hexadecimal. NULL (\"undef\") is returned for data types\nfor which this is not applicable.\n\nLITERALSUFFIX (string)\nCharacters used to suffix a literal. Typically \"\"'\"\" for characters. NULL (\"undef\") is\nreturned for data types where this is not applicable.\n\nCREATEPARAMS (string)\nParameter names for data type definition. For example, \"CREATEPARAMS\" for a \"DECIMAL\" would\nbe \"\"precision,scale\"\" if the DECIMAL type should be declared as\n\"DECIMAL(\"*precision,scale*\")\" where *precision* and *scale* are integer values. For a\n\"VARCHAR\" it would be \"\"max length\"\". NULL (\"undef\") is returned for data types for which\nthis is not applicable.\n\nNULLABLE (integer)\nIndicates whether the data type accepts a NULL value: 0 or an empty string = no, 1 = yes, 2\n= unknown.\n\nCASESENSITIVE (boolean)\nIndicates whether the data type is case sensitive in collations and comparisons.\n\nSEARCHABLE (integer)\nIndicates how the data type can be used in a WHERE clause, as follows:\n\n0 - Cannot be used in a WHERE clause\n1 - Only with a LIKE predicate\n2 - All comparison operators except LIKE\n3 - Can be used in a WHERE clause with any comparison operator\n\nUNSIGNEDATTRIBUTE (boolean)\nIndicates whether the data type is unsigned. NULL (\"undef\") is returned for data types for\nwhich this is not applicable.\n\nFIXEDPRECSCALE (boolean)\nIndicates whether the data type always has the same precision and scale (such as a money\ntype). NULL (\"undef\") is returned for data types for which this is not applicable.\n\nAUTOUNIQUEVALUE (boolean)\nIndicates whether a column of this data type is automatically set to a unique value whenever\na new row is inserted. NULL (\"undef\") is returned for data types for which this is not\napplicable.\n\nLOCALTYPENAME (string)\nLocalized version of the \"TYPENAME\" for use in dialog with users. NULL (\"undef\") is\nreturned if a localized name is not available (in which case \"TYPENAME\" should be used).\n\nMINIMUMSCALE (integer)\nThe minimum scale of the data type. If a data type has a fixed scale, then \"MAXIMUMSCALE\"\nholds the same value. NULL (\"undef\") is returned for data types for which this is not\napplicable.\n\nMAXIMUMSCALE (integer)\nThe maximum scale of the data type. If a data type has a fixed scale, then \"MINIMUMSCALE\"\nholds the same value. NULL (\"undef\") is returned for data types for which this is not\napplicable.\n\nSQLDATATYPE (integer)\nThis column is the same as the \"DATATYPE\" column, except for interval and datetime data\ntypes. For interval and datetime data types, the \"SQLDATATYPE\" field will return\n\"SQLINTERVAL\" or \"SQLDATETIME\", and the \"SQLDATETIMESUB\" field below will return the\nsubcode for the specific interval or datetime data type. If this field is NULL, then the\ndriver does not support or report on interval or datetime subtypes.\n\nSQLDATETIMESUB (integer)\nFor interval or datetime data types, where the \"SQLDATATYPE\" field above is \"SQLINTERVAL\"\nor \"SQLDATETIME\", this field will hold the *subcode* for the specific interval or datetime\ndata type. Otherwise it will be NULL (\"undef\").\n\nAlthough not mentioned explicitly in the standards, it seems there is a simple relationship\nbetween these values:\n\nDATATYPE == (10 * SQLDATATYPE) + SQLDATETIMESUB\n\nNUMPRECRADIX (integer)\nThe radix value of the data type. For approximate numeric types, \"NUMPRECRADIX\" contains\nthe value 2 and \"COLUMNSIZE\" holds the number of bits. For exact numeric types,\n\"NUMPRECRADIX\" contains the value 10 and \"COLUMNSIZE\" holds the number of decimal digits.\nNULL (\"undef\") is returned either for data types for which this is not applicable or if the\ndriver cannot report this information.\n\nINTERVALPRECISION (integer)\nThe interval leading precision for interval types. NULL is returned either for data types\nfor which this is not applicable or if the driver cannot report this information.\n\nFor example, to find the type name for the fields in a select statement you can do:\n\n@names = map { scalar $dbh->typeinfo($)->{TYPENAME} } @{ $sth->{TYPE} }\n\nSince DBI and ODBC drivers vary in how they map their types into the ISO standard types you may\nneed to search for more than one type. Here's an example looking for a usable type to store a\ndate:\n\n$mydatetype = $dbh->typeinfo( [ SQLDATE, SQLTIMESTAMP ] );\n\nSimilarly, to more reliably find a type to store small integers, you could use a list starting\nwith \"SQLSMALLINT\", \"SQLINTEGER\", \"SQLDECIMAL\", etc.\n\nSee also \"Standards Reference Information\".\n\n\"quote\"\n$sql = $dbh->quote($value);\n$sql = $dbh->quote($value, $datatype);\n\nQuote a string literal for use as a literal value in an SQL statement, by escaping any special\ncharacters (such as quotation marks) contained within the string and adding the required type of\nouter quotation marks.\n\n$sql = sprintf \"SELECT foo FROM bar WHERE baz = %s\",\n$dbh->quote(\"Don't\");\n\nFor most database types, at least those that conform to SQL standards, quote would return\n'Don''t' (including the outer quotation marks). For others it may return something like 'Don\\'t'\n\nAn undefined $value value will be returned as the string \"NULL\" (without single quotation marks)\nto match how NULLs are represented in SQL.\n\nIf $datatype is supplied, it is used to try to determine the required quoting behaviour by\nusing the information returned by \"typeinfo\". As a special case, the standard numeric types are\noptimized to return $value without calling \"typeinfo\".\n\nQuote will probably *not* be able to deal with all possible input (such as binary data or data\ncontaining newlines), and is not related in any way with escaping or quoting shell\nmeta-characters.\n\nIt is valid for the quote() method to return an SQL expression that evaluates to the desired\nstring. For example:\n\n$quoted = $dbh->quote(\"one\\ntwo\\0three\")\n\nmay return something like:\n\nCONCAT('one', CHAR(12), 'two', CHAR(0), 'three')\n\nThe quote() method should *not* be used with \"Placeholders and Bind Values\".\n\n\"quoteidentifier\"\n$sql = $dbh->quoteidentifier( $name );\n$sql = $dbh->quoteidentifier( $catalog, $schema, $table, \\%attr );\n\nQuote an identifier (table name etc.) for use in an SQL statement, by escaping any special\ncharacters (such as double quotation marks) it contains and adding the required type of outer\nquotation marks.\n\nUndefined names are ignored and the remainder are quoted and then joined together, typically\nwith a dot (\".\") character. For example:\n\n$id = $dbh->quoteidentifier( undef, 'Her schema', 'My table' );\n\nwould, for most database types, return \"Her schema\".\"My table\" (including all the double\nquotation marks).\n\nIf three names are supplied then the first is assumed to be a catalog name and special rules may\nbe applied based on what \"getinfo\" returns for SQLCATALOGNAMESEPARATOR (41) and\nSQLCATALOGLOCATION (114). For example, for Oracle:\n\n$id = $dbh->quoteidentifier( 'link', 'schema', 'table' );\n\nwould return \"schema\".\"table\"@\"link\".\n\n\"takeimpdata\"\n$impdata = $dbh->takeimpdata;\n\nLeaves the $dbh in an almost dead, zombie-like, state and returns a binary string of raw\nimplementation data from the driver which describes the current database connection. Effectively\nit detaches the underlying database API connection data from the DBI handle. After calling"
},
{
"name": "take_imp_data",
"content": "Why would you want to do this? You don't, forget I even mentioned it. Unless, that is, you're\nimplementing something advanced like a multi-threaded connection pool. See DBI::Pool.\n\nThe returned $impdata can be passed as a \"dbiimpdata\" attribute to a later connect() call,\neven in a separate thread in the same process, where the driver can use it to 'adopt' the\nexisting connection that the implementation data was taken from.\n\nSome things to keep in mind...\n\n* the $impdata holds the only reference to the underlying database API connection data. That\nconnection is still 'live' and won't be cleaned up properly unless the $impdata is used to\ncreate a new $dbh which is then allowed to disconnect() normally.\n\n* using the same $impdata to create more than one other new $dbh at a time may well lead to\nunpleasant problems. Don't do that.\n\nAny child statement handles are effectively destroyed when takeimpdata() is called.\n\nThe \"takeimpdata\" method was added in DBI 1.36 but wasn't useful till 1.49.\n"
},
{
"name": "Database Handle Attributes",
"content": "This section describes attributes specific to database handles.\n\nChanges to these database handle attributes do not affect any other existing or future database\nhandles.\n\nAttempting to set or get the value of an unknown attribute generates a warning, except for\nprivate driver-specific attributes (which all have names starting with a lowercase letter).\n\nExample:\n\n$h->{AutoCommit} = ...; # set/write\n... = $h->{AutoCommit}; # get/read\n\n\"AutoCommit\"\nType: boolean\n\nIf true, then database changes cannot be rolled-back (undone). If false, then database changes\nautomatically occur within a \"transaction\", which must either be committed or rolled back using\nthe \"commit\" or \"rollback\" methods.\n\nDrivers should always default to \"AutoCommit\" mode (an unfortunate choice largely forced on the\nDBI by ODBC and JDBC conventions.)\n\nAttempting to set \"AutoCommit\" to an unsupported value is a fatal error. This is an important\nfeature of the DBI. Applications that need full transaction behaviour can set\n\"$dbh->{AutoCommit} = 0\" (or set \"AutoCommit\" to 0 via \"connect\") without having to check that\nthe value was assigned successfully.\n\nFor the purposes of this description, we can divide databases into three categories:\n\nDatabases which don't support transactions at all.\nDatabases in which a transaction is always active.\nDatabases in which a transaction must be explicitly started (C<'BEGIN WORK'>).\n\n* Databases which don't support transactions at all\n\nFor these databases, attempting to turn \"AutoCommit\" off is a fatal error. \"commit\" and\n\"rollback\" both issue warnings about being ineffective while \"AutoCommit\" is in effect.\n\n* Databases in which a transaction is always active\n\nThese are typically mainstream commercial relational databases with \"ANSI standard\" transaction\nbehaviour. If \"AutoCommit\" is off, then changes to the database won't have any lasting effect\nunless \"commit\" is called (but see also \"disconnect\"). If \"rollback\" is called then any changes\nsince the last commit are undone.\n\nIf \"AutoCommit\" is on, then the effect is the same as if the DBI called \"commit\" automatically\nafter every successful database operation. So calling \"commit\" or \"rollback\" explicitly while\n\"AutoCommit\" is on would be ineffective because the changes would have already been committed.\n\nChanging \"AutoCommit\" from off to on will trigger a \"commit\".\n\nFor databases which don't support a specific auto-commit mode, the driver has to commit each\nstatement automatically using an explicit \"COMMIT\" after it completes successfully (and roll it\nback using an explicit \"ROLLBACK\" if it fails). The error information reported to the\napplication will correspond to the statement which was executed, unless it succeeded and the\ncommit or rollback failed.\n\n* Databases in which a transaction must be explicitly started\n\nFor these databases, the intention is to have them act like databases in which a transaction is\nalways active (as described above).\n\nTo do this, the driver will automatically begin an explicit transaction when \"AutoCommit\" is\nturned off, or after a \"commit\" or \"rollback\" (or when the application issues the next database\noperation after one of those events).\n\nIn this way, the application does not have to treat these databases as a special case.\n\nSee \"commit\", \"disconnect\" and \"Transactions\" for other important notes about transactions.\n\n\"Driver\"\nType: handle\n\nHolds the handle of the parent driver. The only recommended use for this is to find the name of\nthe driver using:\n\n$dbh->{Driver}->{Name}\n\n\"Name\"\nType: string\n\nHolds the \"name\" of the database. Usually (and recommended to be) the same as the\n\"\"dbi:DriverName:...\"\" string used to connect to the database, but with the leading\n\"\"dbi:DriverName:\"\" removed.\n\n\"Statement\"\nType: string, read-only\n\nReturns the statement string passed to the most recent \"prepare\" or \"do\" method called in this\ndatabase handle, even if that method failed. This is especially useful where \"RaiseError\" is\nenabled and the exception handler checks $@ and sees that a 'prepare' method call failed.\n\n\"RowCacheSize\"\nType: integer\n\nA hint to the driver indicating the size of the local row cache that the application would like\nthe driver to use for future \"SELECT\" statements. If a row cache is not implemented, then\nsetting \"RowCacheSize\" is ignored and getting the value returns \"undef\".\n\nSome \"RowCacheSize\" values have special meaning, as follows:\n\n0 - Automatically determine a reasonable cache size for each C