LeetCode Second Highest Salary
阿新 • • 發佈:2018-12-23
Problem
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 |
+---------------------+
即找到第二大的元素。沒有返回null。
MySQL
# Write your MySQL query statement below SELECT (SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMIT 1 OFFSET 1) AS SecondHighestSalary;
分析
通過LIMIT OFFSET找到第二個元素。DISTINCT是為了排除兩個最大值的情況。巢狀是為了解返回null的情況。另一種辦法是使用IFNULL函式。