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 | +------------+----------+--------+
JOIN
and sub-query [Accepted]Algorithm
A top 3 salary in this company means there is no more than 3 salary bigger than itself in the company.
select e1.Name as 'Employee', e1.Salary from Employee e1 where 3 > ( select count(distinct e2.Salary) from Employee e2 where e2.Salary > e1.Salary ) ;
In this code, we count the salary number of which is bigger than e1.Salary. So the output is as below for the sample data.
| Employee | Salary | |----------|--------| | Henry | 80000 | | Max | 90000 | | Randy | 85000 |
Then, we need to join the Employee table with Department in order to retrieve the department information.
MySQL
SELECT d.Name AS 'Department', e1.Name AS 'Employee', e1.Salary FROM Employee e1 JOIN Department d ON e1.DepartmentId = d.Id WHERE 3 > (SELECT COUNT(DISTINCT e2.Salary) FROM Employee e2 WHERE e2.Salary > e1.Salary AND e1.DepartmentId = e2.DepartmentId ) ;
| Department | Employee | Salary | |------------|----------|--------| | IT | Joe | 70000 | | Sales | Henry | 80000 | | Sales | Sam | 60000 | | IT | Max | 90000 | | IT | Randy | 85000 |