题目地址：

https://leetcode.com/problems/employees-earning-more-than-their-managers/

给定一个Employee表，例如：

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

要求返回Salary比自己Manager更高的那些人的Name。例如上表需要返回：

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

可以用FULL OUTER JOIN，也就是先将这个表与自己做笛卡儿积，然后选出ManagerId = Id和e1.Salary > e2.Salary的行的名字即可。代码如下：

SELECT e1.Name AS `Employee` FROM Employee e1 JOIN Employee e2 ON e1.ManagerId = e2.Id AND e1.Salary > e2.Salary

当然也可以这么写：

SELECT e1.Name AS `Employee` FROM Employee e1, Employee e2 WHERE e1.ManagerId = e2.Id AND e1.Salary > e2.Salary