【Leetcode】 Second Highest Salary

题目链接：https://leetcode.com/problems/second-highest-salary/

题目：
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 second highest salary is 200. If there is no second highest salary, then the query should return null.

思路：
子查询

算法：

select max(salary) from Employee where salary<(select max(salary) from Employee)