LeetCode 181. Employees Earning More Than Their Managers

题目描述：
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      |
+----------+

题目大意：
雇员表记录了所有雇员的信息，包括他们的经理在内。每一个雇员都有一个Id，和他的经理的Id。

给定雇员表，编写一个SQL查询找出薪水大于经理的员工姓名。对于上表来说，Joe是唯一收入大于经理的员工。

解题思路：
自连接

SQL语句：

# Write your MySQL query statement below
select a.name as Employee from Employee a,Employee b
    where a.ManagerId = b.Id and a.Salary > b.Salary

原文：
http://bookshadow.com/weblog/2015/01/16/leetcode-employees-earning-more-their-managers/