服务器之家

服务器之家 > 正文

SQL实现LeetCode(185.系里前三高薪水)

时间:2021-09-15 17:35     来源/作者:Grandyang

[LeetCode] 185.Department Top Three Salaries 系里前三高薪水

The Employee table holds all employees. Every employee has an Id, and there is also a column for the department Id.

+----+-------+--------+--------------+
| Id | Name  | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
| 5  | Janet | 69000  | 1            |
| 6  | Randy | 85000  | 1            |
+----+-------+--------+--------------+

The Department table holds all departments of the company.

+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+

Write a SQL query to find employees who earn the top three salaries in each of the department. For the above tables, your SQL query should return the following rows.

+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| IT         | Randy    | 85000  |
| IT         | Joe      | 70000  |
| Sales      | Henry    | 80000  |
| Sales      | Sam      | 60000  |
+------------+----------+--------+

这道题是之前那道Department Highest Salary的拓展,难度标记为Hard,还是蛮有难度的一道题,综合了前面很多题的知识点,首先看使用Select Count(Distinct)的方法,我们内交Employee和Department两张表,然后我们找出比当前薪水高的最多只能有两个,那么前三高的都能被取出来了,参见代码如下:

解法一:

?
1
2
3
4
SELECT d.Name AS Department, e.Name AS Employee, e.Salary FROM Employee e
JOIN Department d on e.DepartmentId = d.Id
WHERE (SELECT COUNT(DISTINCT Salary) FROM Employee WHERE Salary > e.Salary
AND DepartmentId = d.Id) < 3 ORDER BY d.Name, e.Salary DESC;

下面这种方法将上面方法中的<3换成了IN (0, 1, 2),是一样的效果:

解法二:

?
1
2
3
SELECT d.Name AS Department, e.Name AS Employee, e.Salary FROM Employee e, Department d
WHERE (SELECT COUNT(DISTINCT Salary) FROM Employee WHERE Salary > e.Salary
AND DepartmentId = d.Id) IN (0, 1, 2) AND e.DepartmentId = d.Id ORDER BY d.Name, e.Salary DESC;

或者我们也可以使用Group by Having Count(Distinct ..) 关键字来做:

解法三:

?
1
2
3
4
5
SELECT d.Name AS Department, e.Name AS Employee, e.Salary FROM
(SELECT e1.Name, e1.Salary, e1.DepartmentId FROM Employee e1 JOIN Employee e2
ON e1.DepartmentId = e2.DepartmentId AND e1.Salary <= e2.Salary GROUP BY e1.Id
HAVING COUNT(DISTINCT e2.Salary) <= 3) e JOIN Department d ON e.DepartmentId = d.Id
ORDER BY d.Name, e.Salary DESC;

下面这种方法略微复杂一些,用到了变量,跟Consecutive Numbers中的解法三使用的方法一样,目的是为了给每个人都按照薪水的高低增加一个rank,最后返回rank值小于等于3的项即可,参见代码如下:

解法四:

?
1
2
3
4
5
6
7
SELECT d.Name AS Department, e.Name AS Employee, e.Salary FROM
(SELECT Name, Salary, DepartmentId,
@rank := IF(@pre_d = DepartmentId, @rank + (@pre_s <> Salary), 1) AS rank,
@pre_d := DepartmentId, @pre_s := Salary
FROM Employee, (SELECT @pre_d := -1, @pre_s := -1, @rank := 1) AS init
ORDER BY DepartmentId, Salary DESC) e JOIN Department d ON e.DepartmentId = d.Id
WHERE e.rank <= 3 ORDER BY d.Name, e.Salary DESC;

类似题目:

Department Highest Salary

Second Highest Salary

Combine Two Tables

参考资料:

https://leetcode.com/discuss/23002/my-tidy-solution

https://leetcode.com/discuss/91087/yet-another-solution-using-having-count-distinct

https://leetcode.com/discuss/69880/two-solutions-1-count-join-2-three-variables-join

到此这篇关于SQL实现LeetCode(185.系里前三高薪水)的文章就介绍到这了,更多相关SQL实现系里前三高薪水内容请搜索服务器之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持服务器之家!

原文链接:https://www.cnblogs.com/grandyang/p/5367670.html

标签:

相关文章

热门资讯

yue是什么意思 网络流行语yue了是什么梗
yue是什么意思 网络流行语yue了是什么梗 2020-10-11
2020微信伤感网名听哭了 让对方看到心疼的伤感网名大全
2020微信伤感网名听哭了 让对方看到心疼的伤感网名大全 2019-12-26
背刺什么意思 网络词语背刺是什么梗
背刺什么意思 网络词语背刺是什么梗 2020-05-22
苹果12mini价格表官网报价 iPhone12mini全版本价格汇总
苹果12mini价格表官网报价 iPhone12mini全版本价格汇总 2020-11-13
2021年耽改剧名单 2021要播出的59部耽改剧列表
2021年耽改剧名单 2021要播出的59部耽改剧列表 2021-03-05
返回顶部