LeetCode——Employees Earning More Than Their Managers

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

这种单表比较条件，一般都是表内进行join操作.
参照此思路，解题如下所示：

# Write your MySQL query statement belowSELECT     a.Name AS Employee FROM Employee a, Employee bWHERE    a.ManagerId = b.Id    AND a.Salary > b.Salary; 

运行效率在可以接受的范围，此外语句也较为清晰便于维护.