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NAME DBD::CSV - DBI driver for CSV files SYNOPSIS use DBI; # See "Creating database handle" below $dbh = DBI->connect ("dbi:CSV:", undef, undef, { f_ext => ".csv/r", RaiseError => 1, }) or die "Cannot connect: $DBI::errstr"; # Simple statements $dbh->do ("CREATE TABLE foo (id INTEGER, name CHAR (10))"); # Selecting my $sth = $dbh->prepare ("select * from foo"); $sth->execute; $sth->bind_columns (\my ($id, $name)); while ($sth->fetch) { print "id: $id, name: $name\n"; } # Updates my $sth = $dbh->prepare ("UPDATE foo SET name = ? WHERE id = ?"); $sth->execute ("DBI rocks!", 1); $sth->finish; $dbh->disconnect; DESCRIPTION The DBD::CSV module is yet another driver for the DBI (Database independent interface for Perl). This one is based on the SQL "engine" SQL::Statement and the abstract DBI driver DBD::File and implements access to so-called CSV files (Comma Separated Values). Such files are often used for exporting MS Access and MS Excel data. See DBI for details on DBI, SQL::Statement for details on SQL::Statement and DBD::File for details on the base class DBD::File. Prerequisites The only system dependent feature that DBD::File uses, is the "flock ()" function. Thus the module should run (in theory) on any system with a working "flock ()", in particular on all Unix machines and on Windows NT. Under Windows 95 and MacOS the use of "flock ()" is disabled, thus the module should still be usable. Unlike other DBI drivers, you don't need an external SQL engine or a running server. All you need are the following Perl modules, available from any CPAN mirror, for example http://search.cpan.org/ DBI A recent version of the DBI (Database independent interface for Perl). See below why. DBD::File This is the base class for DBD::CSV, and it is part of the DBI distribution. As DBD::CSV requires a matching version of DBD::File which is (partly) developed by the same team that maintains DBD::CSV. See META.json or Makefile.PL for the minimum versions. SQL::Statement A simple SQL engine. This module defines all of the SQL syntax for DBD::CSV, new SQL support is added with each release so you should look for updates to SQL::Statement regularly. It is possible to run "DBD::CSV" without this module if you define the environment variable $DBI_SQL_NANO to 1. This will reduce the SQL support a lot though. See DBI::SQL::Nano for more details. Note that the test suite does only test in this mode in the development environment. Text::CSV_XS This module is used to read and write rows in a CSV file. Installation Installing this module (and the prerequisites from above) is quite simple. The simplest way is to install the bundle: $ cpan Bundle::DBD::CSV Alternatively, you can name them all $ cpan Text::CSV_XS DBI DBD::CSV or even trust "cpan" to resolve all dependencies for you: $ cpan DBD::CSV If you cannot, for whatever reason, use cpan, fetch all modules from CPAN, and build with a sequence like: gzip -d < DBD-CSV-0.40.tgz | tar xf - (this is for Unix users, Windows users would prefer WinZip or something similar) and then enter the following: cd DBD-CSV-0.40 perl Makefile.PL make test If any tests fail, let us know. Otherwise go on with make install UNINST=1 Note that you almost definitely need root or administrator permissions. If you don't have them, read the ExtUtils::MakeMaker man page for details on installing in your own directories. ExtUtils::MakeMaker. Supported SQL Syntax All SQL processing for DBD::CSV is done by SQL::Statement. See SQL::Statement for more specific information about its feature set. Features include joins, aliases, built-in and user-defined functions, and more. See SQL::Statement::Syntax for a description of the SQL syntax supported in DBD::CSV. Table- and column-names are case insensitive unless quoted. Column names will be sanitized unless "raw_header" is true. Using DBD::CSV with DBI For most things, DBD-CSV operates the same as any DBI driver. See DBI for detailed usage. Creating a database handle (connect) Creating a database handle usually implies connecting to a database server. Thus this command reads use DBI; my $dbh = DBI->connect ("dbi:CSV:", "", "", { f_dir => "/home/user/folder", }); The directory tells the driver where it should create or open tables (a.k.a. files). It defaults to the current directory, so the following are equivalent: $dbh = DBI->connect ("dbi:CSV:"); $dbh = DBI->connect ("dbi:CSV:", undef, undef, { f_dir => "." }); $dbh = DBI->connect ("dbi:CSV:f_dir=."); We were told, that VMS might - for whatever reason - require: $dbh = DBI->connect ("dbi:CSV:f_dir="); The preferred way of passing the arguments is by driver attributes: # specify most possible flags via driver flags $dbh = DBI->connect ("dbi:CSV:", undef, undef, { f_schema => undef, f_dir => "data", f_dir_search => [], f_ext => ".csv/r", f_lock => 2, f_encoding => "utf8", csv_eol => "\r\n", csv_sep_char => ",", csv_quote_char => '"', csv_escape_char => '"', csv_class => "Text::CSV_XS", csv_null => 1, csv_bom => 0, csv_tables => { syspwd => { sep_char => ":", quote_char => undef, escape_char => undef, file => "/etc/passwd", col_names => [qw( login password uid gid realname directory shell )], }, }, RaiseError => 1, PrintError => 1, FetchHashKeyName => "NAME_lc", }) or die $DBI::errstr; but you may set these attributes in the DSN as well, separated by semicolons. Pay attention to the semi-colon for "csv_sep_char" (as seen in many CSV exports from MS Excel) is being escaped in below example, as is would otherwise be seen as attribute separator: $dbh = DBI->connect ( "dbi:CSV:f_dir=$ENV{HOME}/csvdb;f_ext=.csv;f_lock=2;" . "f_encoding=utf8;csv_eol=\n;csv_sep_char=\\;;" . "csv_quote_char=\";csv_escape_char=\\;csv_class=Text::CSV_XS;" . "csv_null=1") or die $DBI::errstr; Using attributes in the DSN is easier to use when the DSN is derived from an outside source (environment variable, database entry, or configure file), whereas specifying entries in the attribute hash is easier to read and to maintain. The default value for "csv_binary" is 1 (True). The default value for "csv_auto_diag" is <1>. Note that this might cause trouble on perl versions older than 5.8.9, so up to and including perl version 5.8.8 it might be required to use ";csv_auto_diag=0" inside the "DSN" or "csv_auto_diag =" 0> inside the attributes. Creating and dropping tables You can create and drop tables with commands like the following: $dbh->do ("CREATE TABLE $table (id INTEGER, name CHAR (64))"); $dbh->do ("DROP TABLE $table"); Note that currently only the column names will be stored and no other data. Thus all other information including column type (INTEGER or CHAR (x), for example), column attributes (NOT NULL, PRIMARY KEY, ...) will silently be discarded. This may change in a later release. A drop just removes the file without any warning. See DBI for more details. Table names cannot be arbitrary, due to restrictions of the SQL syntax. I recommend that table names are valid SQL identifiers: The first character is alphabetic, followed by an arbitrary number of alphanumeric characters. If you want to use other files, the file names must start with "/", "./" or "../" and they must not contain white space. Inserting, fetching and modifying data The following examples insert some data in a table and fetch it back: First, an example where the column data is concatenated in the SQL string: $dbh->do ("INSERT INTO $table VALUES (1, ". $dbh->quote ("foobar") . ")"); Note the use of the quote method for escaping the word "foobar". Any string must be escaped, even if it does not contain binary data. Next, an example using parameters: $dbh->do ("INSERT INTO $table VALUES (?, ?)", undef, 2, "It's a string!"); Note that you don't need to quote column data passed as parameters. This version is particularly well designed for loops. Whenever performance is an issue, I recommend using this method. You might wonder about the "undef". Don't wonder, just take it as it is. :-) It's an attribute argument that I have never used and will be passed to the prepare method as the second argument. To retrieve data, you can use the following: my $query = "SELECT * FROM $table WHERE id > 1 ORDER BY id"; my $sth = $dbh->prepare ($query); $sth->execute (); while (my $row = $sth->fetchrow_hashref) { print "Found result row: id = ", $row->{id}, ", name = ", $row->{name}; } $sth->finish (); Again, column binding works: The same example again. my $sth = $dbh->prepare (qq; SELECT * FROM $table WHERE id > 1 ORDER BY id; ;); $sth->execute; my ($id, $name); $sth->bind_columns (undef, \$id, \$name); while ($sth->fetch) { print "Found result row: id = $id, name = $name\n"; } $sth->finish; Of course you can even use input parameters. Here's the same example for the third time: my $sth = $dbh->prepare ("SELECT * FROM $table WHERE id = ?"); $sth->bind_columns (undef, \$id, \$name); for (my $i = 1; $i <= 2; $i++) { $sth->execute ($id); if ($sth->fetch) { print "Found result row: id = $id, name = $name\n"; } $sth->finish; } See DBI for details on these methods. See SQL::Statement for details on the WHERE clause. Data rows are modified with the UPDATE statement: $dbh->do ("UPDATE $table SET id = 3 WHERE id = 1"); Likewise you use the DELETE statement for removing rows: $dbh->do ("DELETE FROM $table WHERE id > 1"); Error handling In the above examples we have never cared about return codes. Of course, this is not recommended. Instead we should have written (for example): my $sth = $dbh->prepare ("SELECT * FROM $table WHERE id = ?") or die "prepare: " . $dbh->errstr (); $sth->bind_columns (undef, \$id, \$name) or die "bind_columns: " . $dbh->errstr (); for (my $i = 1; $i <= 2; $i++) { $sth->execute ($id) or die "execute: " . $dbh->errstr (); $sth->fetch and print "Found result row: id = $id, name = $name\n"; } $sth->finish ($id) or die "finish: " . $dbh->errstr (); Obviously this is tedious. Fortunately we have DBI's *RaiseError* attribute: $dbh->{RaiseError} = 1; $@ = ""; eval { my $sth = $dbh->prepare ("SELECT * FROM $table WHERE id = ?"); $sth->bind_columns (undef, \$id, \$name); for (my $i = 1; $i <= 2; $i++) { $sth->execute ($id); $sth->fetch and print "Found result row: id = $id, name = $name\n"; } $sth->finish ($id); }; $@ and die "SQL database error: $@"; This is not only shorter, it even works when using DBI methods within subroutines. DBI database handle attributes Metadata The following attributes are handled by DBI itself and not by DBD::File, thus they all work as expected: Active ActiveKids CachedKids CompatMode (Not used) InactiveDestroy Kids PrintError RaiseError Warn (Not used) The following DBI attributes are handled by DBD::File: AutoCommit Always on ChopBlanks Works NUM_OF_FIELDS Valid after "$sth->execute" NUM_OF_PARAMS Valid after "$sth->prepare" NAME NAME_lc NAME_uc Valid after "$sth->execute"; undef for Non-Select statements. NULLABLE Not really working. Always returns an array ref of one's, as DBD::CSV does not verify input data. Valid after "$sth->execute"; undef for non-Select statements. These attributes and methods are not supported: bind_param_inout CursorName LongReadLen LongTruncOk DBD-CSV specific database handle attributes In addition to the DBI attributes, you can use the following dbh attributes: DBD::File attributes f_dir This attribute is used for setting the directory where CSV files are opened. Usually you set it in the dbh and it defaults to the current directory ("."). However, it may be overridden in statement handles. f_dir_search This attribute optionally defines a list of extra directories to search when opening existing tables. It should be an anonymous list or an array reference listing all folders where tables could be found. my $dbh = DBI->connect ("dbi:CSV:", "", "", { f_dir => "data", f_dir_search => [ "ref/data", "ref/old" ], f_ext => ".csv/r", }) or die $DBI::errstr; f_ext This attribute is used for setting the file extension. f_schema This attribute allows you to set the database schema name. The default is to use the owner of "f_dir". "undef" is allowed, but not in the DSN part. my $dbh = DBI->connect ("dbi:CSV:", "", "", { f_schema => undef, f_dir => "data", f_ext => ".csv/r", }) or die $DBI::errstr; f_encoding This attribute allows you to set the encoding of the data. With CSV, it is not possible to set (and remember) the encoding on a column basis, but DBD::File now allows the encoding to be set on the underlying file. If this attribute is not set, or undef is passed, the file will be seen as binary. f_lock With this attribute you can specify a locking mode to be used (if locking is supported at all) for opening tables. By default, tables are opened with a shared lock for reading, and with an exclusive lock for writing. The supported modes are: 0 Force no locking at all. 1 Only shared locks will be used. 2 Only exclusive locks will be used. But see "KNOWN BUGS" in DBD::File. DBD::CSV specific attributes csv_class The attribute *csv_class* controls the CSV parsing engine. This defaults to "Text::CSV_XS", but "Text::CSV" can be used in some cases, too. Please be aware that "Text::CSV" does not care about any edge case as "Text::CSV_XS" does and that "Text::CSV" is probably about 100 times slower than "Text::CSV_XS". In order to use the specified class other than "Text::CSV_XS", it needs to be loaded before use. "DBD::CSV" does not "require"/"use" the specified class itself. Text::CSV_XS specific attributes csv_eol csv_sep_char csv_quote_char csv_escape_char csv_csv The attributes *csv_eol*, *csv_sep_char*, *csv_quote_char* and *csv_escape_char* are corresponding to the respective attributes of the *csv_class* (usually Text::CSV_CS) object. You may want to set these attributes if you have unusual CSV files like /etc/passwd or MS Excel generated CSV files with a semicolon as separator. Defaults are "\015\012"", ",", """ and """, respectively. The *csv_eol* attribute defines the end-of-line pattern, which is better known as a record separator pattern since it separates records. The default is windows-style end-of-lines "\015\012" for output (writing) and unset for input (reading), so if on unix you may want to set this to newline ("\n") like this: $dbh->{csv_eol} = "\n"; It is also possible to use multi-character patterns as record separators. For example this file uses newlines as field separators (sep_char) and the pattern "\n__ENDREC__\n" as the record separators (eol): name city __ENDREC__ joe seattle __ENDREC__ sue portland __ENDREC__ To handle this file, you'd do this: $dbh->{eol} = "\n__ENDREC__\n" , $dbh->{sep_char} = "\n" The attributes are used to create an instance of the class *csv_class*, by default Text::CSV_XS. Alternatively you may pass an instance as *csv_csv*, the latter takes precedence. Note that the *binary* attribute *must* be set to a true value in that case. Additionally you may overwrite these attributes on a per-table base in the *csv_tables* attribute. csv_null With this option set, all new statement handles will set "always_quote" and "blank_is_undef" in the CSV parser and writer, so it knows how to distinguish between the empty string and "undef" or "NULL". You cannot reset it with a false value. You can pass it to connect, or set it later: $dbh = DBI->connect ("dbi:CSV:", "", "", { csv_null => 1 }); $dbh->{csv_null} = 1; csv_bom With this option set, the CSV parser will try to detect BOM (Byte Order Mark) in the header line. This requires Text::CSV_XS version 1.22 or higher. $dbh = DBI->connect ("dbi:CSV:", "", "", { csv_bom => 1 }); $dbh->{csv_bom} = 1; csv_tables This hash ref is used for storing table dependent metadata. For any table it contains an element with the table name as key and another hash ref with the following attributes: o All valid attributes to the CSV parsing module. Any of them can optionally be prefixed with "csv_". o All attributes valid to DBD::File If you pass it "f_file" or its alias "file", "f_ext" has no effect, but "f_dir" and "f_encoding" still have. csv_tables => { syspwd => { # Table name csv_sep_char => ":", # Text::CSV_XS quote_char => undef, # Text::CSV_XS escape_char => undef, # Text::CSV_XS f_dir => "/etc", # DBD::File f_file => "passwd", # DBD::File col_names => # DBD::File [qw( login password uid gid realname directory shell )], }, }, csv_* All other attributes that start with "csv_" and are not described above will be passed to "Text::CSV_XS" (without the "csv_" prefix). These extra options are only likely to be useful for reading (select) handles. Examples: $dbh->{csv_allow_whitespace} = 1; $dbh->{csv_allow_loose_quotes} = 1; $dbh->{csv_allow_loose_escapes} = 1; See the "Text::CSV_XS" documentation for the full list and the documentation. Driver specific attributes f_file The name of the file used for the table; defaults to "$dbh->{f_dir}/$table" eol sep_char quote_char escape_char class csv These correspond to the attributes *csv_eol*, *csv_sep_char*, *csv_quote_char*, *csv_escape_char*, *csv_class* and *csv_csv*. The difference is that they work on a per-table basis. col_names skip_first_row By default DBD::CSV assumes that column names are stored in the first row of the CSV file and sanitizes them (see "raw_header" below). If this is not the case, you can supply an array ref of table names with the *col_names* attribute. In that case the attribute *skip_first_row* will be set to FALSE. If you supply an empty array ref, the driver will read the first row for you, count the number of columns and create column names like "col0", "col1", ... Note that column names that match reserved SQL words will cause unwanted and sometimes confusing errors. If your CSV has headers that match reserved words, you will require these two attributes. If "test.csv" looks like select,from 1,2 the select query would result in "select select, from from test;", which obviously is illegal SQL. raw_header Due to the SQL standard, field names cannot contain special characters like a dot (".") or a space (" ") unless the column names are quoted. Following the approach of mdb_tools, all these tokens are translated to an underscore ("_") when reading the first line of the CSV file, so all field names are 'sanitized'. If you do not want this to happen, set "raw_header" to a true value and the entries in the first line of the CSV data will be used verbatim for column headers and field names. DBD::CSV cannot guarantee that any part in the toolchain will work if field names have those characters, and the chances are high that the SQL statements will fail. Currently, the sanitizing of headers is as simple as s/\W/_/g; Note that headers (column names) might be folded in other parts of the code stack, specifically SQL::Statement, whose docs mention: Wildcards are expanded to lower cased identifiers. This might confuse some people, but it was easier to implement. That means that in my $sth = $dbh->prepare ("select * from foo"); $sth->execute; while (my $row = $sth->fetchrow_hashref) { say for keys %$row; } all keys will show as all lower case, regardless of the original header. It's strongly recommended to check the attributes supported by "Metadata" in DBD::File. Example: Suppose you want to use /etc/passwd as a CSV file. :-) There simplest way is: use DBI; my $dbh = DBI->connect ("dbi:CSV:", undef, undef, { f_dir => "/etc", csv_sep_char => ":", csv_quote_char => undef, csv_escape_char => undef, }); $dbh->{csv_tables}{passwd} = { col_names => [qw( login password uid gid realname directory shell )]; }; $sth = $dbh->prepare ("SELECT * FROM passwd"); Another possibility where you leave all the defaults as they are and override them on a per table basis: require DBI; my $dbh = DBI->connect ("dbi:CSV:"); $dbh->{csv_tables}{passwd} = { eol => "\n", sep_char => ":", quote_char => undef, escape_char => undef, f_file => "/etc/passwd", col_names => [qw( login password uid gid realname directory shell )], }; $sth = $dbh->prepare ("SELECT * FROM passwd"); Driver private methods These methods are inherited from DBD::File: data_sources The "data_sources" method returns a list of sub-directories of the current directory in the form "dbi:CSV:directory=$dirname". If you want to read the sub-directories of another directory, use my $drh = DBI->install_driver ("CSV"); my @list = $drh->data_sources (f_dir => "/usr/local/csv_data"); list_tables This method returns a list of file-names inside $dbh->{directory}. Example: my $dbh = DBI->connect ("dbi:CSV:directory=/usr/local/csv_data"); my @list = $dbh->func ("list_tables"); Note that the list includes all files contained in the directory, even those that have non-valid table names, from the view of SQL. See "Creating and dropping tables" above. KNOWN ISSUES * The module is using flock () internally. However, this function is not available on some platforms. Use of flock () is disabled on MacOS and Windows 95: There's no locking at all (perhaps not so important on these operating systems, as they are for single users anyways). TODO Tests Aim for a full 100% code coverage - eol Make tests for different record separators. - csv_xs Test with a variety of combinations for sep_char, quote_char, and escape_char testing - quoting $dbh->do ("drop table $_") for DBI-tables (); - errors Make sure that all documented exceptions are tested. . write to write-protected file . read from badly formatted csv . pass bad arguments to csv parser while fetching Add tests that specifically test DBD::File functionality where that is useful. RT Attack all open DBD::CSV bugs in RT CPAN::Forum Attack all items in http://www.cpanforum.com/dist/DBD-CSV Documentation Expand on error-handling, and document all possible errors. Use Text::CSV_XS::error_diag () wherever possible. Debugging Implement and document dbd_verbose. Data dictionary Investigate the possibility to store the data dictionary in a file like .sys$columns that can store the field attributes (type, key, nullable). Examples Make more real-life examples from the docs in examples/ SEE ALSO DBI, Text::CSV_XS, SQL::Statement, DBI::SQL::Nano For help on the use of DBD::CSV, see the DBI users mailing list: http://lists.cpan.org/showlist.cgi?name=dbi-users For general information on DBI see http://dbi.perl.org/ and http://faq.dbi-support.com/ AUTHORS and MAINTAINERS This module is currently maintained by H.Merijn Brand <h.m.brand AT xs4all.nl> in close cooperation with and help from Jens Rehsack <sno AT NetBSD.org> The original author is Jochen Wiedmann. Previous maintainer was Jeff Zucker COPYRIGHT AND LICENSE Copyright (C) 2009-2021 by H.Merijn Brand Copyright (C) 2004-2009 by Jeff Zucker Copyright (C) 1998-2004 by Jochen Wiedmann All rights reserved. You may distribute this module under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.
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