181. Employees Earning More Than Their Managers(Lettcode)

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

大意是找出比Manager工资高的Employee，首先想到的是自连接，可博主大概是头疼脑热。。写了个子查询的代码
还为此纠结了半天，写此博文来警醒自己。下面贴代码
select e1.Name as Employee
from Employee e1,Employee e2
where e1.ManagerId = e2.Id and e1.Salary > e2.Salary;

或者内连接也可以
select e1.Name as Employee
from Employee e1 inner join Employee e2
on e1.ManagerId = e2.Id and e1.Salary > e2.Salary;