BEGIN(7)		PostgreSQL 9.2.24 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(7) or ROLLBACK(7) 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 (SET_TRANSACTION(7)) 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 (START_TRANSACTION(7)) has the same functionality as
       BEGIN.

       Use COMMIT(7) or ROLLBACK(7) 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 (START_TRANSACTION(7)), whose
       reference page contains additional compatibility information.

       The DEFERRABLEtransaction_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 9.2.24		  2017-11-06			      BEGIN(7)