181. Employees Earning More Than Their Managers

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问题描述

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

题目链接：

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思路分析

找到Employee表中，工资比自己manager高的员工。

使用subquery，对于employee中的每一条记录，去找对应的manager的salary进行比对。

代码

# Write your MySQL query statement below
select e.Name as Employee from Employee e where e.salary > (select salary from Employee where Id = e.ManagerId)

时间复杂度：未知
空间复杂度：未知

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反思

不使用subquery，直接在where中写好条件

# Write your MySQL query statement below
select e1.Name as Employee from Employee e1 ,Employee e2 where e1.ManagerId = e2.Id and e1.salary > e2.salary