Triggers

Triggers are a special type of stored procedure that is automatically called when a certain action is performed on a table. For example, we can use triggers to perform an action when a row is inserted into a table, deleted from it, or data is modified.

Triggers are similar to functions and stored procedures in the sense that they have a body that is executed when the trigger is called.

The AFTER triggers

Triggers are called when there is a change in a table’s state. For example, a trigger may be executed after a row is deleted from a table.

Syntax

There are three types of AFTER triggers:

• AFTER DELETE means that this trigger is executed when a row is deleted from the TableName table:

  CREATE TRIGGER TriggerName
  ON TableName
  AFTER DELETE
  AS
      [Trigger body]
  

• AFTER INSERT means that the trigger is called after a new row is inserted into a table:

  CREATE TRIGGER TriggerName
  ON

...