BEGIN(7) PostgreSQL 9.3.4 Documentation BEGIN(7)NAMEBEGIN - start a transaction block
SYNOPSISBEGIN [ 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
DESCRIPTIONBEGIN 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;
COMPATIBILITYBEGIN 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 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 ALSOCOMMIT(7), ROLLBACK(7), START TRANSACTION (START_TRANSACTION(7)),
SAVEPOINT(7)PostgreSQL 9.3.4 2014 BEGIN(7)