为什么这个触发器不按我想要的方式工作？

Question

我的mysql数据库中有两个表： 顾问：身份证 学生：顾问ID |主要

我想更新学生，其中Advisor中已删除的ID等于advisorID，并使用一组if语句根据该学生的专业更改该学生的advisorID值。这就是我到目前为止所做的：

    delimiter //
    create trigger advisor_delete after delete
    on advisor
        UPDATE Student
            IF Student.major = 'major1' THEN SET Student.advisorID = 1;
            ELSEIF Student.major = 'major2' THEN SET Student.advisorID = 2;
            ELSEIF Student.major = 'major3' THEN SET Student.advisorID = 3;
            ELSE SET Student.advisorID = 4;
            ENDIF;
        WHERE Student.advisorID = OLD.id;
    end//

欢迎任何帮助。感谢。

Answer 1

我不知道这种UPDATE/IF ELSEIF语法，但CASE语句适合您：

delimiter //
create trigger advisor_delete after delete
on advisor
    UPDATE Student
        SET Student.advisorID = 
            CASE Student.major WHEN 'major1' THEN 1
                               WHEN 'major2' THEN 2
                               WHEN 'major3' THEN 3
                               ELSE 4
            END
    WHERE Student.advisorID = OLD.id;
end//