Triggers

A Trigger is a procedure that initiates an action when an event(Such as insert, update, or delete) occurs. It is stored and managed by the Database Management Systems. It is used to maintain the referential integrity of data by changing the data in a systematic fashion. A trigger cannot be called or executed; it automatically fires when data modification occurs.

Nested Trigger: A trigger that contains insert, update, and delete logic within logic within itself is called a nested trigger.