Source

• leetcode: 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      |
+----------+

MySQL

-- select e1.Name
-- from Employee e1, Employee e2
-- where e1.managerId=e2.Id and e1.Salary>e2.Salary

select e1.Name
from Employee e1
join Employee e2
on e1.managerId=e2.Id and e1.Salary>e2.Salary