地址:https://leetcode-cn.com/problems/second-highest-salary/solution/di-er-gao-de-xin-shui-by-leetcode/
## 编写一个 SQL 查询,获取 Employee 表中第二高的薪水(Salary) 。 示例: +----+--------+ | Id | Salary | +----+--------+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +----+--------+ 例如上述 Employee 表,SQL查询应该返回 200 作为第二高的薪水。如果不存在第二高的薪水,那么查询应返回 null。 +---------------------+ | SecondHighestSalary | +---------------------+ | 200 | +---------------------+ `解题思路` 1 limit 或者OFFSET select IFNULL((select distinct(Salary) from Employee order by Salary desc limit 1,1),null) as SecondHighestSalary 2 嵌套表查询 `select max(Salary) SecondHighestSalary from employee where salary<(select max(salary) from employee)`