LeetCode: 185. Department Top Three Salaries

题目描述

The Employee table holds all employees. Every employee has an Id, and there is also a column for the 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 | +----+-------+--------+--------------+

The Department table holds all departments of the company.

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

Write a SQL query to find employees who earn the top three salaries in each of the department. For the above tables, your SQL query should return the following rows.

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

解题思路

每取一条记录，就判断其薪水是否是前三。如果是，则保留。

AC 代码

SELECT D.Name AS Department, E1.Name AS Employee, E1.Salary AS Salary FROM Employee AS E1 INNER JOIN Department AS D ON E1.DepartmentId = D.Id WHERE 3 > (SELECT COUNT(DISTINCT E2.Salary) FROM Employee AS E2 WHERE E1.DepartmentId = E2.DepartmentId AND E1.Salary < E2.Salary)