SQL實現(xiàn)LeetCode(181.員工掙得比經(jīng)理多)
[LeetCode] 181.Employees Earning More Than Their Managers 員工掙得比經(jīng)理多
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 |
+----------+
這道題給我們了一個Employee表,里面有員工的薪水信息和其經(jīng)理的信息,經(jīng)理也屬于員工,其經(jīng)理Id為空,讓我們找出薪水比其經(jīng)理高的員工,那么就是一個很簡單的比較問題了,我們可以生成兩個實例對象進(jìn)行內(nèi)交通過ManagerId和Id,然后限制條件是一個Salary大于另一個即可:
解法一:
SELECT e1.Name FROM Employee e1 JOIN Employee e2 ON e1.ManagerId = e2.Id WHERE e1.Salary > e2.Salary;
我們也可以不用Join,直接把條件都寫到where里也行:
解法二:
SELECT e1.Name FROM Employee e1, Employee e2 WHERE e1.ManagerId = e2.Id AND e1.Salary > e2.Salary;
參考資料:
https://leetcode.com/discuss/88189/two-straightforward-way-using-where-and-join
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