創建觸發器MySQL更新員工表中的工資

Question

如何創建觸發器MySQL更新員工表中的薪水並將薪金列中的舊值替換爲old_salary列？

Answer 1

見CREATE TRIGGER Syntax：

create trigger salary_trigger 
    before update on employee 
    for each row begin 
     if new.salary != old.salary then 
      set new.old_salary = old.salary 
     end if; 
    end;