Source: 

Description:

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 |+------------+----------+--------+

 

Solution:

select t2.name  as Department, t1.Employee , t1.salary from (    select e1.id, e1.name as employee, e1.salary, e1.departmentid from Employee  e1    inner join  Employee e2    on e1.departmentid = e2.departmentid    and e1.salary<=e2.salary    group by e1.id    having count(distinct(e2.salary))<=3)t1inner join(select * from Department )t2on t1.DepartmentId  = t2.id