employees-earning-more-than-their-managers.sql

'''

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

'''



# Write your MySQL query statement below

# method one  where 语句
# select
#     a.name AS 'Employee'
# from
#     Employee AS a,
#     Employee AS b
# where
#     a.ManagerId = b.Id
#         AND a.Salary > b.Salary


# method two join 语句

SELECT
     a.name AS 'Employee'
FROM Employee AS a JOIN Employee AS b
     ON a.ManagerId = b.Id
     AND a.Salary > b.Salary