Leetcode day3 employees who exceed the manager's income

181. Employees who earn more than their managers

The difficulty is simple

SQL framework

Employee Table contains all employees , Their manager also belongs to the staff . Every employee has one Id, In addition, there is a list of managers corresponding to employees Id.

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

Given Employee surface , Write a SQL Inquire about , This query can get the names of employees who earn more than their managers . In the table above ,Joe It's the only employee who earns more than his manager .

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

Answer key ：

The implementation of this problem is relatively simple , You only need a self table connection to complete this operation

1、 First, query all the data connected from the table .

select * from Employee a1 
left join Employee a2 
on a1.Managerid = a2.id 

The operation results are shown in the following table

a1.id	a1.name	a1.salary	a1.ManagerId	a2.id	a2.name	a2.salary	a2.ManagerId
1	Joe	70000	3	3	Sam	60000	Null
2	Henry	80000	4	4	Max	90000	Null
3	Sam	60000	Null	Null	Null	Null	Null
4	Max	90000	Null	Null	Null	Null	Null

2、 We just need to judge and find out a1.salary The value is greater than a2.salary The value of the a1.name That's all right.

select a1.Name as Employee from Employee a1 
left join Employee a2 
on a1.Managerid = a2.id 
where a1.Salary > a2.Salary

Running results ：

Employee : Joe