The word ‘Trigger’ means to activate. In PL/SQL, the trigger is a stored procedure that defines an action taken by the database when the database-related event is performed.
Triggers are mainly required for the following purposes :
* To maintain complex integrity constraints
* Auditing table information by recording the changes
* Signaling other program actions when changes are made to the table
* Enforcing complex business rules
* Preventing invalid transactions
