2002-07-26START TRANSACTIONSQL - Language StatementsSTART TRANSACTIONstart a transaction block
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ]
1998-09-27
Inputs
None.
1998-09-27
Outputs
START TRANSACTION
Message returned if successful.
WARNING: BEGIN: already a transaction in progress
If there is already a transaction in progress when the
command is issued.
Description
This command begins a new transaction. If the isolation level is
specified, the new transaction has that isolation level. In all other
respects, the behavior of this command is identical to the
command.
Notes
The isolation level of a transaction can also be set with the
command. If no isolation level is specified, the default isolation
level is used.
CompatibilitySQL99
is the default isolation level in
SQL99, but it is not the usual default in
PostgreSQL: the factory default setting
is READ COMMITTED.
PostgreSQL
does not provide the isolation levels
and . Because of lack of predicate
locking, the level is
not truly serializable. See the User's Guide
for details.
In SQL99 this statement can specify two other
properties of the new transaction: whether the transaction is
read-only and the size of the diagnostics area. Neither of these
concepts are currently supported in
PostgreSQL.