set_constraints

SET CONSTRAINTS()		 SQL Commands		    SET CONSTRAINTS()



NAME
       SET CONSTRAINTS - set the constraint mode of the current transaction


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


DESCRIPTION
       SET CONSTRAINTS sets the behavior of constraint evaluation in the cur-
       rent transaction. In IMMEDIATE mode, constraints are  checked  at  the
       end  of	each statement. In DEFERRED mode, constraints are not checked
       until transaction commit.

       When you change the mode of a constraint to be IMMEDIATE, the new con-
       straint	mode takes effect retroactively: any outstanding data modifi-
       cations that would have been checked at the  end	 of  the  transaction
       (when  using DEFERRED) are instead checked during the execution of the
       SET CONSTRAINTS command.

       Upon creation, a constraint is always give one of  three	 characteris-
       tics: INITIALLY DEFERRED, INITIALLY IMMEDIATE DEFERRABLE, or INITIALLY
       IMMEDIATE NOT DEFERRABLE. The third class is not affected by  the  SET
       CONSTRAINTS command.

       Currently,  only foreign key constraints are affected by this setting.
       Check and unique constraints are always effectively initially  immedi-
       ate not deferrable.

NOTES
       This  command  only alters the behavior of constraints within the cur-
       rent transaction. Thus, if you  execute	this  command  outside	of  a
       transaction  block (BEGIN/COMMIT pair), it will not appear to have any
       effect. If you wish to change the behavior  of  a  constraint  without
       needing to issue a SET CONSTRAINTS command in every transaction, spec-
       ify INITIALLY DEFERRED or INITIALLY IMMEDIATE when you create the con-
       straint.

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	  2008-01-03		    SET CONSTRAINTS()