题目：
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 | +----------+这个解决方法好像是叫自连接？
select E1.Name from Employee as E1, Employee as E2 where E1.ManagerId = E2.Id and E1.Salary > E2.Salary 评论里说内连接的速度可以快一点
select a.Name from Employee a inner join Employee b on a.ManagerId=b.Id where a.Salary>b.Salary
还有一位大哥说，因为不需要没有经理的员工 所以可以这样
SELECT e1.`Name` FROM `Employee` e1 LEFT JOIN `Employee` e2 ON (e2.`Id` = e1.`ManagerId`) WHERE e1.`ManagerId` IS NOT NULL AND e1.`Salary` > e2.`Salary`事实上inner join已经做到这一点了 INNER JOIN 关键字在表中存在至少一个匹配时返回行。
拓展阅读：
sql内连接、外连接和自连接查询
http://blog.csdn.net/zdp072/article/details/42458569
