LeetCode-Second Highest Salary

##题目

####Second Highest Salary

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.

##解题思路
该题是找到表中第二大的值，首先我们可以找到最大的值，然后再在比最大值小的值中找到最大的那个即可。

##算法代码
代码采用mysql实现：

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# Write your MySQL query statement below
select max(Salary) from Employee
where Salary < (select max(Salary) from Employee)