mysql - 关于写SQL查询的问题

Question

假设我有两个表/列:

Employee - > EmpId, DeptNo, EmpName, Salary
Department -> DeptNo, DeptName

编写查询以获取所有部门中薪水最高的员工姓名。 我试过这个:

Select max(salary),empname 
from Employee 
where deptno = (select deptno 
                from department
                where deptname in('isd','it','sales')

是否正确？其实是一道面试题。

Answer 1

这是 groupwise max 的示例MySQL模式。一种方法是:

    SELECT e.salary, e.name, d.deptname
    FROM Employee AS e 
     JOIN (
       SELECT max(salary) AS max_sal, deptno
       FROM Employee
       GROUP BY deptno
     ) AS d_max ON (e.salary=d_max.max_sal AND e.deptno=d_max.deptno)
     JOIN Department AS d ON (e.deptno = d_max.deptno)

如果一个部门有多个员工拥有最高薪水，它会为一个部门返回不止一行