mysql - 我希望具有 zreo 值的 Studentid 表字段不被插入，我通过使用触发器来执行此操作，但它仍然允许插入它们

Question

仍然允许插入零值..

    CREATE TRIGGER check_my_constraint BEFORE insert ON `personal_details`
         FOR EACH ROW 
         BEGIN
         DECLARE msg varchar(255);
         IF (NEW.studentid<0)
         THEN
            SET msg = concat('Constraint my_constraint violated: studentid must not be zero ', cast(new.studentid as char));
            SIGNAL sqlstate '45000' SET message_text = msg;
         END IF; 
         END ;

Answer 1

您仅检查小于零。您必须检查小于或等于零:

IF (NEW.studentid <= 0)