CREATE_CONSTRAINT_TRIGGER - define a new constraint trigger
SYNOPSIS
CREATE CONSTRAINT TRIGGER name
AFTER event [ OR ... ]
ON table_name
[ FROM referenced_table_name ]
{ NOT DEFERRABLE | [ DEFERRABLE ] { INITIALLY IMMEDIATE | INITIALLY DEFERRED } }
FOR EACH ROW
[ WHEN ( condition ) ]
EXECUTE PROCEDURE function_name ( arguments )
DESCRIPTION
CREATE CONSTRAINT TRIGGER
creates a
constraint trigger. This is the same as a regular trigger except that the timing of the trigger firing can be adjusted using
SET CONSTRAINTS (SET_CONSTRAINTS(7)). Constraint triggers must be
AFTER ROW
triggers. They can be fired either at the end of the statement causing the triggering event, or at the end of the containing transaction; in the latter case they are said to be
deferred. A pending deferred-trigger firing can also be forced to happen immediately by using
SET CONSTRAINTS.
PARAMETERS
name
The name of the constraint trigger. This is also the name to use when modifying the trigger's behavior using
SET CONSTRAINTS. The name cannot be schema-qualified --- the trigger inherits the schema of its table.
event
One of
INSERT,
UPDATE, or
DELETE; this specifies the event that will fire the trigger. Multiple events can be specified using
OR.
table_name
The (possibly schema-qualified) name of the table in which the triggering events occur.
referenced_table_name
The (possibly schema-qualified) name of another table referenced by the constraint. This option is used for foreign-key constraints and is not recommended for general use.
DEFERRABLE, NOT DEFERRABLE, INITIALLY IMMEDIATE, INITIALLY DEFERRED
The default timing of the trigger. See the
CREATE TABLE (CREATE_TABLE(7))
documentation for details of these constraint options.
condition
A Boolean expression that determines whether the trigger function will actually be executed. This acts the same as in
CREATE TRIGGER (CREATE_TRIGGER(7)). Note in particular that evaluation of the
WHEN
condition is not deferred, but occurs immediately after the row update operation is performed. If the condition does not evaluate to
true
then the trigger is not queued for deferred execution.
function_name
The function to call when the trigger is fired. See
CREATE TRIGGER (CREATE_TRIGGER(7))
for details.
arguments
Optional argument strings to pass to the trigger function. See
CREATE TRIGGER (CREATE_TRIGGER(7))
for details.
COMPATIBILITY
CREATE CONSTRAINT TRIGGER
is a
PostgreSQL
extension of the
SQL
standard.