What is a Trigger?

A trigger is a sql block structure which is fired when a DML statements like Insert, Delete, Update is executed on a database table. A trigger is triggered automatically when an associated DML statement is executed.


The Syntax for creating a trigger is:

CREATE [OR REPLACE ] TRIGGER trigger_name 

{BEFORE | AFTER | INSTEAD OF } 

{INSERT [OR] | UPDATE [OR] | DELETE} 

[OF col_name] 

ON table_name 

[REFERENCING OLD AS o NEW AS n] 

[FOR EACH ROW] 

WHEN (condition)  

BEGIN 

--- sql statements  

END;