Mimicking Check Constraints in MySQL

check_constraints_mysql.sql

-- Modified from: http://stackoverflow.com/a/14248038/956779
-- Add a BEFORE INSERT constraint that only allows values between 1 and 5
DELIMITER $$
CREATE TRIGGER `test_before_insert` BEFORE INSERT ON cheese_shop.items
FOR EACH ROW
BEGIN
    IF (NEW.ratings > 5 OR NEW.ratings < 1) THEN
    SIGNAL SQLSTATE '12345'
        SET MESSAGE_TEXT = 'check constraint on items.ratings failed';
    END IF;
END$$   
DELIMITER ;  

-- Add a BEFORE UPDATE constraint that only allows values between 1 and 5
DELIMITER $$
CREATE TRIGGER `test_before_update` BEFORE UPDATE ON cheese_shop.items
FOR EACH ROW
BEGIN
    IF (NEW.ratings > 5 OR NEW.ratings < 1) THEN
    SIGNAL SQLSTATE '12345'
        SET MESSAGE_TEXT = 'check constraint on items.ratings failed';
    END IF;
END$$   
DELIMITER ;