Mysql如何创建相等约束？

CREATE TABLE example (
    id INT PRIMARY KEY,
    value1 INT,
    value2 INT,
    CHECK (value1 = value2)
);

DELIMITER //

CREATE TRIGGER check_values_before_insert
BEFORE INSERT ON example
FOR EACH ROW
BEGIN
    IF NEW.value1 != NEW.value2 THEN
        SIGNAL SQLSTATE '45000'
        SET MESSAGE_TEXT = 'value1 and value2 must be equal';
    END IF;
END//

DELIMITER ;

DELIMITER //

CREATE PROCEDURE insert_example(IN p_id INT, IN p_value INT)
BEGIN
    DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
    BEGIN
        ROLLBACK;
        RESIGNAL;
    END;

    START TRANSACTION;
    INSERT INTO example (id, value1, value2) VALUES (p_id, p_value, p_value);
    COMMIT;
END//

DELIMITER ;