[SQL : 서브쿼리 / INNER JOIN / WINDOW FUNCTION ] LeetCode: 185. Department Top Three Salaries

185. Department Top Three Salaries

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>> 문제

 

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   | 85000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
| 5  | Janet | 69000  | 1            |
| 6  | Randy | 85000  | 1            |
| 7  | Will  | 70000  | 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 (order of rows does not matter).

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

Explanation:

In IT department, Max earns the highest salary, both Randy and Joe earn the second highest salary, and Will earns the third highest salary. There are only two employees in the Sales department, Henry earns the highest salary while Sam earns the second highest salary.

 

* 봉급 순위 TOP 3 을 뽑는 문제 

 

>> 문제 해결 코드

SELECT t.department
        , t.employee
        , t.salary
FROM (
    SELECT department.name as department
            , employee.name as employee
            , employee.salary as salary
            , DENSE_RANK() OVER ( PARTITION BY employee.departmentid ORDER BY salary DESC )  as dr  
    FROM employee
        INNER JOIN department ON employee.departmentid = department.id
    ) t 
WHERE t.dr <= 3

 

: SELECT 절안에, DENSE_RANK ( ) 의 결과를 그냥 받을 수 없으므로, 서브쿼리를 사용해준다.

 

 

leetcode.com/problems/department-top-three-salaries/

Department Top Three Salaries - LeetCode