SQL Coding Exercise – Employees Earning More Than Their Managers

The SQL Coding Exercise is from oj-leet Online Judge and you can submit your solution to this problem here: https://oj.leetcode.com/problems/employees-earning-more-than-their-managers/

The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.

+----+-------+--------+-----------+
| Id | Name  | Salary | ManagerId |
+----+-------+--------+-----------+
| 1  | Joe   | 70000  | 3         |
| 2  | Henry | 80000  | 4         |
| 3  | Sam   | 60000  | NULL      |
| 4  | Max   | 90000  | NULL      |
+----+-------+--------+-----------+

Given the Employee table, write a SQL query that finds out employees who earn more than their managers. For the above table, Joe is the only employee who earns more than his manager.

+----------+
| Employee |
+----------+
| Joe      |
+----------+

The same table can be used twice, and then we have a straightforward solution:

select `a`.`Name` from `Employee` as `a`, `Employee` as `b` where `a`.`Salary` > `b`.`Salary` and `a`.`ManagerId` = `b`.`Id`

You could also use [left join] which gives the same result:

select a.Name
from Employee a inner join Employee b on a.ManagerId = b.Id
where a.Salary > b.Salary

–EOF (The Ultimate Computing & Technology Blog) —