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      |
+----------+
思路一：用exists

SELECT Name from Employee e1 where EXISTS (SELECT ID FROM Employee e2 where e1.ManagerId = e2.Id AND e1.Salary > e2.Salary);

自连接

SELECT e1.Name FROM Employee e1 LEFT JOIN Employee e2 ON e1.ManagerId = e2.Id WHERE e1.Salary > e2.Salary;