Employee 表包含所有員工信息，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信息。
+----+----------+ | 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 e2 where e2.DepartmentId=d.Id 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）。
括號里面是查詢在這部門中工資比他高的人的數量。
找出每個部門工資最高的員工
select d.Name Department,e1.Name Employee,e1.Salary
from Employee e1,Department d where e1.DepartmentId=d.Id
and Salary in (select max(Salary) from Employee e2 where e1.DepartmentId=e2.DepartmentId)