trigger-operation: INSERTING | DELETING | UPDATING [ ( column-name-string ) ] | UPDATE ( column-name )
Trigger-operation conditions can be used only in triggers, to carry out actions depending on the kind of action that caused the trigger to fire.
The argument for UPDATING is a quoted string (for example, UPDATING( 'mycolumn' )
). The argument for UPDATE is an identifier (for example, UPDATE( mycolumn )
). The two versions are interoperable, and are included for compatibility with SQL dialects of other vendors' DBMS.
If you supply an UPDATING or UPDATE function, you must also supply a REFERENCING clause in the CREATE TRIGGER statement to avoid syntax errors.
The following trigger displays a message showing which action caused the trigger to fire.
CREATE TRIGGER tr BEFORE INSERT, UPDATE, DELETE ON sample_table REFERENCING OLD AS t1old FOR EACH ROW BEGIN DECLARE msg varchar(255); SET msg = 'This trigger was fired by an '; IF INSERTING THEN SET msg = msg || 'insert' ELSEIF DELETING THEN set msg = msg || 'delete' ELSEIF UPDATING THEN set msg = msg || 'update' END IF; MESSAGE msg TO CLIENT END; |
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