refactor 569

Author: fishercoder1534

Diff for: database/_569.sql

@@ -1,40 +1,3 @@
---569. Median Employee Salary
--- The Employee table holds all employees. The employee table has three columns: Employee Id, Company Name, and Salary.
---
---+-----+------------+--------+
---|Id   | Company    | Salary |
---+-----+------------+--------+
---|1    | A          | 2341   |
---|2    | A          | 341    |
---|3    | A          | 15     |
---|4    | A          | 15314  |
---|5    | A          | 451    |
---|6    | A          | 513    |
---|7    | B          | 15     |
---|8    | B          | 13     |
---|9    | B          | 1154   |
---|10   | B          | 1345   |
---|11   | B          | 1221   |
---|12   | B          | 234    |
---|13   | C          | 2345   |
---|14   | C          | 2645   |
---|15   | C          | 2645   |
---|16   | C          | 2652   |
---|17   | C          | 65     |
---+-----+------------+--------+
---
---Write a SQL query to find the median salary of each company. Bonus points if you can solve it without using any built-in SQL functions.
---
---+-----+------------+--------+
---|Id   | Company    | Salary |
---+-----+------------+--------+
---|5    | A          | 451    |
---|6    | A          | 513    |
---|12   | B          | 234    |
---|9    | B          | 1154   |
---|14   | C          | 2645   |
---+-----+------------+--------+
-
 select Id, Company, Salary from
 (
 select e.Id, e.Salary, e.Company,  if( @prev = e.Company , @Rank := @Rank + 1, @Rank := 1) as rank, @prev := e.Company