题目链接:https://leetcode.com/problems/second-highest-salary/
编写一个 SQL 查询,获取 Employee 表中第二高的薪水(Salary) 。
+----+--------+ | 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 | +---------------------+
思路:
用distinct去重,然后用limit取出特定大小的那一个元素,注意元素不存在的情况。
select (
select DISTINCT
salary
from Employee order by salary desc limit 1,1)
as SecondHighestSalary
方法二:
用ifnull函数:
SELECT IFNULL( (SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMIT 1 , 1), NULL) AS SecondHighestSalary