create_trigger man page on IRIX

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     CREATE TRIGGERSQL - Language Statements (2002-11CREATE TRIGGER(l)

     NAME
	  CREATE TRIGGER - define a new trigger

     SYNOPSIS
	  CREATE TRIGGER name { BEFORE | AFTER } { event [OR ...] }
	      ON table FOR EACH { ROW | STATEMENT }
	      EXECUTE PROCEDURE func ( arguments )

	INPUTS
	  name The name to give the new trigger. This must be distinct
	       from the name of any other trigger for the same table.

	  event
	       One of INSERT, DELETE or UPDATE.

	  table
	       The name (optionally schema-qualified) of the table the
	       trigger is for.

	  func A user-supplied function that is declared as taking no
	       arguments and returning type trigger.

	  arguments
	       An optional comma-separated list of arguments to be
	       provided to the function when the trigger is executed,
	       along with the standard trigger data such as old and
	       new tuple contents. The arguments are literal string
	       constants. Simple names and numeric constants may be
	       written here too, but they will all be converted to
	       strings.

	OUTPUTS
	  CREATE TRIGGER
	       This message is returned if the trigger is successfully
	       created.

     DESCRIPTION
	  CREATE TRIGGER will enter a new trigger into the current
	  data base. The trigger will be associated with the relation
	  table and will execute the specified function func.

	  The trigger can be specified to fire either before BEFORE
	  the operation is attempted on a tuple (before constraints
	  are checked and the INSERT, UPDATE or DELETE is attempted)
	  or AFTER the operation has been attempted (e.g., after
	  constraints are checked and the INSERT, UPDATE or DELETE has
	  completed). If the trigger fires before the event, the
	  trigger may skip the operation for the current tuple, or
	  change the tuple being inserted (for INSERT and UPDATE
	  operations only). If the trigger fires after the event, all

     Page 1					     (printed 3/24/03)

     CREATE TRIGGERSQL - Language Statements (2002-11CREATE TRIGGER(l)

	  changes, including the last insertion, update, or deletion,
	  are ``visible'' to the trigger.

	  If multiple triggers of the same kind are defined for the
	  same event, they will be fired in alphabetical order by
	  name.

	  SELECT does not modify any rows so you can not create SELECT
	  triggers. Rules and views are more appropriate in such
	  cases.

	  Refer to the chapters on SPI and Triggers in the PostgreSQL
	  Programmer's Guide for more information.

     NOTES
	  To create a trigger on a table, the user must have the
	  TRIGGER privilege on the table.

	  In PostgreSQL versions before 7.3, it was necessary to
	  declare trigger functions as returning the placeholder type
	  opaque, rather than trigger. To support loading of old dump
	  files, CREATE TRIGGER will accept a function declared as
	  returning opaque, but it will issue a NOTICE and change the
	  function's declared return type to trigger.

	  As of the current release, STATEMENT triggers are not
	  implemented.

	  Refer to the DROP TRIGGER [drop_trigger(l)] command for
	  information on how to remove triggers.

     EXAMPLES
	  Check if the specified distributor code exists in the
	  distributors table before appending or updating a row in the
	  table films:

	  CREATE TRIGGER if_dist_exists
	      BEFORE INSERT OR UPDATE ON films FOR EACH ROW
	      EXECUTE PROCEDURE check_primary_key ('did', 'distributors', 'did');

	  Before cancelling a distributor or updating its code, remove
	  every reference to the table films:

	  CREATE TRIGGER if_film_exists
	      BEFORE DELETE OR UPDATE ON distributors FOR EACH ROW
	      EXECUTE PROCEDURE check_foreign_key (1, 'CASCADE', 'did', 'films', 'did');

	  The second example can also be done by using a foreign key,
	  constraint as in:

     Page 2					     (printed 3/24/03)

     CREATE TRIGGERSQL - Language Statements (2002-11CREATE TRIGGER(l)

	  CREATE TABLE distributors (
	      did      DECIMAL(3),
	      name     VARCHAR(40),
	      CONSTRAINT if_film_exists
	      FOREIGN KEY(did) REFERENCES films
	      ON UPDATE CASCADE ON DELETE CASCADE
	  );

     COMPATIBILITY
	  SQL92
	       There is no CREATE TRIGGER statement in SQL92.

	  SQL99
	       The CREATE TRIGGER statement in PostgreSQL implements a
	       subset of the SQL99 standard. The following
	       functionality is missing:

	       o SQL99 allows triggers to fire on updates to specific
		 columns (e.g., AFTER UPDATE OF col1, col2).

	       o SQL99 allows you to define aliases for the ``old''
		 and ``new'' rows or tables for use in the definition
		 of the triggered action (e.g., CREATE TRIGGER ... ON
		 tablename REFERENCING OLD ROW AS somename NEW ROW AS
		 othername ...). Since PostgreSQL allows trigger
		 procedures to be written in any number of user-
		 defined languages, access to the data is handled in a
		 language-specific way.

	       o PostgreSQL only has row-level triggers, no
		 statement-level triggers.

	       o PostgreSQL only allows the execution of a stored
		 procedure for the triggered action.  SQL99 allows the
		 execution of a number of other SQL commands, such as
		 CREATE TABLE as triggered action.  This limitation is
		 not hard to work around by creating a stored
		 procedure that executes these commands.

	  SQL99 specifies that multiple triggers should be fired in
	  time-of-creation order. PostgreSQL uses name order, which
	  was judged more convenient to work with.

     SEE ALSO
	  CREATE FUNCTION [create_function(l)], ALTER TRIGGER
	  [alter_trigger(l)], DROP TRIGGER [drop_trigger(l)],
	  PostgreSQL Programmer's Guide

     Page 3					     (printed 3/24/03)

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