爲什麼這個觸發器不按我想要的方式工作？

Question

我在我的mysql數據庫中有兩個表： 顧問：編號 學生：advisorID |主要

我想更新學生，其中Advisor中刪除的ID等於advisorID並使用一組if語句來根據該學生的專業更改該學生的advisorID值。這是我迄今爲止：

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// 

任何幫助是值得歡迎的。謝謝。

Answer 1

我不知道這UPDATE/IFELSEIF語法，但CASE聲明會爲你工作：

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//