SET 
CONSTRAINTS(7)						   SQL Commands 						SET CONSTRAINTS(7)

NAME

       SET CONSTRAINTS - set constraint checking modes for the current transaction

SYNOPSIS

       SET CONSTRAINTS { ALL | name [, ...] } { DEFERRED | IMMEDIATE }

DESCRIPTION

       SET  CONSTRAINTS  sets  the behavior of constraint checking within the current transaction. IMMEDIATE constraints are checked at the end of
       each statement. DEFERRED constraints are not checked until transaction commit. Each constraint has its own IMMEDIATE or DEFERRED mode.

       Upon creation, a constraint is given one of three characteristics: DEFERRABLE INITIALLY DEFERRED, DEFERRABLE INITIALLY  IMMEDIATE,  or  NOT
       DEFERRABLE.  The  third	class  is  always  IMMEDIATE and is not affected by the SET CONSTRAINTS command. The first two classes start every
       transaction in the indicated mode, but their behavior can be changed within a transaction by SET CONSTRAINTS.

       SET CONSTRAINTS with a list of constraint names changes the mode of just those constraints (which must  all  be	deferrable).  The  current
       schema  search  path  is  used  to find the first matching name if no schema name is specified. SET CONSTRAINTS ALL changes the mode of all
       deferrable constraints.

       When SET CONSTRAINTS changes the mode of a constraint from DEFERRED to IMMEDIATE, the new mode takes effect retroactively: any  outstanding
       data  modifications  that  would  have  been checked at the end of the transaction are instead checked during the execution of the SET CON-
       STRAINTS command.  If any such constraint is violated, the SET CONSTRAINTS fails (and does not change the constraint mode). Thus, SET  CON-
       STRAINTS can be used to force checking of constraints to occur at a specific point in a transaction.

       Currently,  only  foreign key constraints are affected by this setting. Check and unique constraints are always effectively not deferrable.
       Triggers that are declared as ``constraint triggers'' are also affected.

NOTES

       This command only alters the behavior of constraints within the current transaction. Thus, if you execute this command outside of a  trans-
       action block (BEGIN/COMMIT pair), it will not appear to have any effect.

COMPATIBILITY

       This command complies with the behavior defined in the SQL standard, except for the limitation that, in PostgreSQL, it only applies to for-
       eign-key constraints.

SQL - Language Statements					    2010-05-14							SET CONSTRAINTS(7)