mysql查詢每個部門/班級前幾名

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Employee 表包含所有員工資訊，每個員工有其對應的 Id, salary 和 department Id 。

+----+-------+--------+--------------+| Id | Name  | Salary | DepartmentId |+----+-------+--------+--------------+| 1  | Joe   | 70000  | 1            || 2  | Henry | 80000  | 2            || 3  | Sam   | 60000  | 2            || 4  | Max   | 90000  | 1            || 5  | Janet | 69000  | 1            || 6  | Randy | 85000  | 1            |+----+-------+--------+--------------+

Department 表包含公司所有部門的資訊。

+----+----------+| Id | Name     |+----+----------+| 1  | IT       || 2  | Sales    |+----+----------+

編寫一個 SQL 查詢，找出每個部門工資前三高的員工。例如，根據上述給定的表格，查詢結果應返回：

+------------+----------+--------+| Department | Employee | Salary |+------------+----------+--------+| IT         | Max      | 90000  || IT         | Randy    | 85000  || IT         | Joe      | 70000  || Sales      | Henry    | 80000  || Sales      | Sam      | 60000  |+------------+----------+--------+

select d.Name Department,e1.Name Employee,e1.Salary
from Employee e1,Department d where e1.DepartmentId=d.Id and
(select count(distinct e2.Salary) from Employee e1,Employee e2 where e1.DepartmentId=e2.DepartmentId and e2.Salary>e1.Salary)<3
order by d.Name,e1.Salary DESC

意思就是：我們要查詢的這個人，在這部門中工資比他高的少於3個人（0,1,2人）。
括弧裡面是查詢在這部門中工資比他高的人的數量。

mysql查詢每個部門/班級前幾名