man > BEGIN(7)

BEGIN(7)                           PostgreSQL 16.14 Documentation                           BEGIN(7)

NAME
       BEGIN - start a transaction block

SYNOPSIS
       BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]

       where transaction_mode is one of:

           ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
           READ WRITE | READ ONLY
           [ NOT ] DEFERRABLE

DESCRIPTION
       BEGIN initiates a transaction block, that is, all statements after a BEGIN command will be
       executed in a single transaction until an explicit COMMIT or ROLLBACK is given. By default
       (without BEGIN), PostgreSQL executes transactions in “autocommit” mode, that is, each
       statement is executed in its own transaction and a commit is implicitly performed at the end
       of the statement (if execution was successful, otherwise a rollback is done).

       Statements are executed more quickly in a transaction block, because transaction start/commit
       requires significant CPU and disk activity. Execution of multiple statements inside a
       transaction is also useful to ensure consistency when making several related changes: other
       sessions will be unable to see the intermediate states wherein not all the related updates
       have been done.

       If the isolation level, read/write mode, or deferrable mode is specified, the new transaction
       has those characteristics, as if SET TRANSACTION was executed.

PARAMETERS
       WORK
       TRANSACTION
           Optional key words. They have no effect.

       Refer to SET TRANSACTION (SET_TRANSACTION(7)) for information on the meaning of the other
       parameters to this statement.

NOTES
       START TRANSACTION has the same functionality as BEGIN.

       Use COMMIT or ROLLBACK to terminate a transaction block.

       Issuing BEGIN when already inside a transaction block will provoke a warning message. The
       state of the transaction is not affected. To nest transactions within a transaction block,
       use savepoints (see SAVEPOINT(7)).

       For reasons of backwards compatibility, the commas between successive transaction_modes can
       be omitted.

EXAMPLES
       To begin a transaction block:

           BEGIN;

COMPATIBILITY
       BEGIN is a PostgreSQL language extension. It is equivalent to the SQL-standard command START
       TRANSACTION, whose reference page contains additional compatibility information.

       The DEFERRABLE transaction_mode is a PostgreSQL language extension.

       Incidentally, the BEGIN key word is used for a different purpose in embedded SQL. You are
       advised to be careful about the transaction semantics when porting database applications.

SEE ALSO
       COMMIT(7), ROLLBACK(7), START TRANSACTION (START_TRANSACTION(7)), SAVEPOINT(7)

PostgreSQL 16.14                                2026                                        BEGIN(7)