Employee 表包含所有员工，他们的经理也属于员工。每个员工都有一个 Id，此外还有一列对应员工的经理的 Id。
+----+-------+--------+-----------+ | Id | Name | Salary | ManagerId | +----+-------+--------+-----------+ | 1 | Joe | 70000 | 3 | | 2 | Henry | 80000 | 4 | | 3 | Sam | 60000 | NULL | | 4 | Max | 90000 | NULL | +----+-------+--------+-----------+
给定 Employee 表，编写一个 SQL 查询，该查询可以获取收入超过他们经理的员工的姓名。在上面的表格中，Joe 是唯一一个收入超过他的经理的员工。
+----------+ | Employee | +----------+ | Joe | +----------+
答案:
select * FROM employee AS a, employee AS b where a.ManagerId = b.Id and a.Salary > b.Salary
拓展:选出有经理的员工即manageredId不为空
select Id from employee where ManagerId is not null
:当where中id对应有多个值的时候使用in 查出不为空的经理的薪水
select ManagerId from employee where Id in (select Id from employee where ManagerId is not null)