【sql】統計工資大於主管工資的員工名

Employees Earning More Than Their Managers

問題：

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

解決：

① 生成兩個實例對象進行內交經過ManagerId和Id，而後限制條件是一個Salary大於另外一個便可。2139 ms

SELECT e1.Name Employee
FROM Employee e1 JOIN Employee e2 ON e1.ManagerId = e2.Id
WHERE e1.Salary > e2.Salary;

② 能夠不用Join，直接把條件都寫到where裏也行。1487 ms

SELECT e1.Name Employee FROM Employee e1,Employee e2
WHERE e1.ManagerId = e2.Id AND e1.Salary > e2.Salary;