1.

Why use triggers in MySQL?

Answer»

In MySQL, a trigger corresponds to a set of actions running AUTOMATICALLY when a PARTICULAR change OPERATION like SQL INSERT, UPDATE, or DELETE query is performed on a table.

Example

CREATE TRIGGER data_backup BEFORE UPDATE ON users
   FOR EACH ROW
   BEGIN
     IF NEW.amount < 0 THEN
        SET NEW.amount = 0;
     ELSEIF NEW.amount > 100 THEN
       SET NEW.amount = 100;
     END IF;
   END;//



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