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인프런 - SQL 고급 강의 듣고 공부 06 _ WINDOW함수로 풀기 #29

Open hdonghun opened 2 years ago

hdonghun commented 2 years ago

LeetCode -185. Department Top Three Salaries 출처 : https://leetcode.com/problems/department-top-three-salaries/

Table: Employee +--------------+---------+ | Column Name | Type | +--------------+---------+ | id | int | | name | varchar | | salary | int | | departmentId | int | +--------------+---------+ id is the primary key column for this table. departmentId is a foreign key of the ID from the Department table. Each row of this table indicates the ID, name, and salary of an employee. It also contains the ID of their department.

Table: Department +-------------+---------+ | Column Name | Type | +-------------+---------+ | id | int | | name | varchar | +-------------+---------+ id is the primary key column for this table. Each row of this table indicates the ID of a department and its name. A company's executives are interested in seeing who earns the most money in each of the company's departments. A high earner in a department is an employee who has a salary in the top three unique salaries for that department. Write an SQL query to find the employees who are high earners in each of the departments. Return the result table in any order.

The query result format is in the following example. Example 1: Input: Employee table: +----+-------+--------+--------------+ | 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 | +----+-------+--------+--------------+ Department table: +----+-------+ | id | name | +----+-------+ | 1 | IT | | 2 | Sales | +----+-------+

Output: +------------+----------+--------+ | Department | Employee | Salary | +------------+----------+--------+ | IT | Max | 90000 | | IT | Joe | 85000 | | IT | Randy | 85000 | | IT | Will | 70000 | | Sales | Henry | 80000 | | Sales | Sam | 60000 | +------------+----------+--------+ Explanation: In the IT department:

In the Sales department:

hdonghun commented 2 years ago

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