[SQL]LeetCode177. 第N高的薪水 | Nth Highest Salary

★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
➤微信公衆號：山青詠芝（shanqingyongzhi）
➤博客園地址：山青詠芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：http://www.javashuo.com/article/p-vcymjmog-md.html 
➤若是連接不是山青詠芝的博客園地址，則多是爬取做者的文章。
➤原文已修改更新！強烈建議點擊原文地址閱讀！支持做者！支持原創！
★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★

Write a SQL query to get the nth highest salary from the Employee table.

+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+

For example, given the above Employee table, the nth highest salary where n = 2 is 200. If there is no nth highest salary, then the query should return null.

+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| 200                    |
+------------------------+

---

編寫一個 SQL 查詢，獲取 Employee 表中第 n 高的薪水（Salary）。

+----+--------+
| Id | Salary |
+----+--------+
| 1  | 100    |
| 2  | 200    |
| 3  | 300    |
+----+--------+

例如上述 Employee 表，n = 2 時，應返回第二高的薪水 200。若是不存在第 n 高的薪水，那麼查詢應返回 null。

+------------------------+
| getNthHighestSalary(2) |
+------------------------+
| 200                    |
+------------------------+

---

140ms

1 CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
2 BEGIN
3     set N = N-1;
4   RETURN (
5       # Write your MySQL query statement below.
6       select distinct Salary from Employee order by Salary desc limit N,1
7   );
8 END

---

149ms

 1 CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
 2 BEGIN
 3   set N = N-1;
 4   RETURN (      
 5       select distinct Salary as 'getNthHighestSalary(2)'
 6       from Employee
 7       order by Salary desc
 8       limit N, 1
 9   );
10 END