START
TRANSACTION(7) SQL Commands START TRANSACTION(7)
NAME
START TRANSACTION - start a transaction block
SYNOPSIS
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ]
INPUTS
None.
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 BEGIN [begin(7)] command.
NOTES
The isolation level of a transaction can also be set with the SET TRANSACTION [set_transaction(7)] command. If no isolation level is speci-
fied, the default isolation level is used.
COMPATIBILITY
SQL99
SERIALIZABLE 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 READ UNCOMMITTED and REPEATABLE READ. Because of lack of predicate locking,
the SERIALIZABLE 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.
SQL - Language Statements 2002-07-26 START TRANSACTION(7)
