leetcode_gym/_problems/sql_second_highest_salary.md

layout, title, last_solved, category, leetcode_url, status

layout	title	last_solved	category	leetcode_url	status
page	SQL - Second Highest Salary (limit/offset + ifnull)		sql	https://leetcode.com/problems/second-highest-salary	Attempted

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                 |
+---------------------+

Solution

Normally something like this is sufficient if you just use the limit and offset clause.

{% highlight sql %}

select distinct salary as SecondHighestSalary from employee order by salary desc limit 1 offset 1

{% endhighlight %}

Without limit, the resultset is

300
200
100

• offset chooses the one you want and puts it on the top
• limit just selects the top one

But we also have to use the ifnull( if this is null , return this value ) clause

{% highlight sql %}

select ifnull(

(select distinct salary as SecondHighestSalary
from employee
order by salary desc
limit 1 offset 1)

,
null ) as SecondHighestSalary

{% endhighlight %}