MYSQL抛出异常+禁止删除触发器、同步插入触发器

DROP TRIGGER IF EXISTS m;
CREATE TRIGGER m AFTER DELETE ON test.m FOR EACH ROW
BEGIN
DECLARE	msg VARCHAR (255);
IF old.count = 2 THEN -- old为伪记录
SET msg = "sc中有记录无法删除";
SIGNAL SQLSTATE 'HY000' SET mysql_errno = 22, message_text = msg;-- HY000为系统内部错误号，22为自定义的显示错误号，msg为错误文本
END IF;
END;

插入一表另一表同步插入

DROP TRIGGER IF EXISTS t;

CREATE TRIGGER t

AFTER INSERT ON tab1

FOR EACH ROW

BEGIN

insert into tab2(tab2_id) values(new.tab1_id);

END