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BEGIN()
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

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
  [commit(5)] or ROLLBACK [rollback(l)] 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 or read/write mode is specified, the new transaction
  has those characteristics, as if SET TRANSACTION [set_transaction(5)] was
  executed.

PARAMETERS
  WORK

  TRANSACTION
       Optional key words. They have no effect.

  Refer to SET TRANSACTION [set_transaction(5)] for information on the
  meaning of the other parameters to this statement.

NOTES
  START TRANSACTION [start_transaction(5)] has the same functionality as
  BEGIN.

  Use COMMIT [commit(5)] or ROLLBACK [rollback(5)] 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
  [savepoint(5)]).

  For reasons of backwards compatibility, the commas between successive
  transaction_modes may 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(5)], which see for
  additional compatibility information.

  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 [commit(5)], ROLLBACK [rollback(l)], START TRANSACTION
  [start_transaction(l)], SAVEPOINT [savepoint(l)]

Index for Section 5

Alphabetical listing for B

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