What is MYSQL Trigger?

A trigger is a rule that you put on a table which basically says, whenever you DELETE, UPDATE or INSERT something in this table, also do something else.

DROP TRIGGER IF EXISTS deleteUser;
DELIMITER |
CREATE TRIGGER deleteUser AFTER DELETE ON ul_logins
FOR EACH ROW BEGIN
  DELETE FROM userbase WHERE userID = old.id;
END;
|
DELIMITER ;

DELIMITER | 

CREATE TRIGGER `after_insert_cart_items`

AFTER INSERT ON `trigger_cart_items` 

FOR EACH ROW

    BEGIN

        INSERT INTO trigger_cart_log (cart_id, item_id)

        VALUES (NEW.cart_id, NEW.item_id);

    END

|
DELIMITER ;

DELIMITER | 

CREATE TRIGGER `after_update_cost`

    AFTER UPDATE ON `trigger_items_cost` FOR EACH ROW

    BEGIN

       UPDATE trigger_items

       SET price = (NEW.cost * 1.3)

       WHERE item_id = NEW.item_id;

    END

|
DELIMITER ;

CREATE TRIGGER `before_update_cost`

    BEFORE UPDATE ON `trigger_items_cost` FOR EACH ROW

    BEGIN

        IF NEW.cost < 50 THEN

            SET NEW.cost = 50;

        ELSEIF NEW.cost > 50 AND NEW.cost < 100 THEN

            SET NEW.cost = 100;

        END IF;

    END