Q; How can create trigger and What benefit triggers?

Ans: A Trigger is a named database object which defines some action that the database should take when some databases related event occurs. Triggers are executed when you issues a data manipulation command like INSERT, DELETE, UPDATE on a table for which the trigger has been created. They are automatically executed and also transparent to the user. But for creating the trigger the user must have the CREATE TRIGGER privilege. In this section we will describe you about the syntax to create and drop the triggers and describe you some examples of how to use them.

CREATE TRIGGER
The general syntax of CREATE TRIGGER is :
  CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name FOR EACH ROW trigger_statement

delimiter //

CREATE TRIGGER updtrigger BEFORE UPDATE ON Employee

    -> FOR EACH ROW

    -> BEGIN

    -> IF NEW.Salary<=500 THEN

    -> SET NEW.Salary=10000;

    -> ELSEIF NEW.Salary>500 THEN

    -> SET NEW.Salary=15000;

    -> END IF;

    -> END

delimiter ;

UPDATE Employee

    -> SET Salary=500;