Question

我正在学习如何在MYSQL中构建触发器，我已经构建了一个触发器，如果其中一个部门员工被更新（他们的工资被更新或者他们被添加到部门/从部门移除），它将重新计算部门工资。如果我更新用户的工资，它也不会更新部门工资。

员工表：

SSN
Salary
Name
Dno
Supervisor_ssn

部门表：

DName
Dno
Total_sal
Manager_SSN

触发器如下所示：

DELIMITER $$
CREATE TRIGGER `Employee_AUPD` AFTER UPDATE ON `Employee` FOR EACH ROW
BEGIN
 IF old.salary != new.salary THEN
    UPDATE department SET total_sal = total_sal - old.salary
        WHERE new.dno = department.dno;
    UPDATE department SET total_sal = total_sal + new.salary
        WHERE new.dno = department.dno;
 END IF;
 IF old.dno != new.dno THEN
    UPDATE department SET total_sal = total_sal - old.salary
        WHERE old.dno = department.dno;
    UPDATE department SET total_sal = total_sal + new.salary
        WHERE new.dno = department.dno;
 END IF;
END;
DELIMITER;

Answer 1

您有逻辑错误。如果工资和部门发生变化，则第一个IF块会从新部门中减去旧工资。

但你不需要测试任何东西。只需对这两个更新语句进行编码：

UPDATE department SET
total_sal = total_sal - old.salary
WHERE department.dno = old.dno;

UPDATE department SET
total_sal = total_sal + new.salary
WHERE department.dno = new.dno;

这种逻辑是睿智的，不会失败。

更新触发器...不按预期工作？

1 个答案: