LeetCode: 176. Second Highest Salary

题目描述

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

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

For example, given the above Employee table, the query should return 200 as the second highest salary. If there is no second highest salary, then the query should return null.

+---------------------+
| SecondHighestSalary | +---------------------+
| 200 | +---------------------+

解题思路

首先找到最高薪水，然后将最高薪水表和薪水表连接。在新表中 Salary < SecondHighestSalary 的最大值就是所求的第二高薪水。

AC 代码

# Write your MySQL query statement below
select MAX(Salary) as SecondHighestSalary from (select MAX(Salary) as HighestSalary from Employee) as HS, -- 最高薪水表 Employee as E where HS.HighestSalary > E.Salary;