LeetCode 176: Second Highest Salary

Date: January 14, 2026
Category: SQL
Time Taken: 10 minutes
Difficulty: Medium

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Problem Statement

Write a solution to find the second highest distinct salary from the Employee table. If there is no second-highest salary, return null.

Link: Second Highest Salary

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My Approach

Initial thought:

• I thought of using OFFSET and LIMIT in ORDER BY to get the second-highest salary, but in case of no second-highest salary, this solution will not return null.

• Another brute force-ish solution would be to use CTE/subquery to find the second max salary less than the first max salary.

Final solution:
The best solution would be to use DENSE_RANK() and give every different salary a different rank, and we can just get the salary whose rank = 2. But it would still not return null; to accomplish that, we will add a SELECT statement wrapper at the end.

Why this works:
This works because this is a scalable solution; we just need to change the value of rank, and we can get the Nth highest salary.

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Solution Code (Subquery)

SELECT MAX(salary) AS SecondHighestSalary
FROM Employee
WHERE salary < (SELECT MAX(salary) AS s1 FROM Employee)

Solution Code (Dense_rank)

SELECT (
    SELECT DISTINCT salary
    FROM (
        SELECT salary , DENSE_RANK() OVER(ORDER BY salary DESC) AS rnk
        FROM Employee
        ) AS ranked
    WHERE rnk = 2
    ) AS secondHighestSalary

Key Takeaway: Whenever we need to get the Nth row from data, we should prefer window functions first.

Pattern: Window Functions

Mistakes I Made: I considered solving this without window functions, but I should have realized it would require a window function solution. I also had trouble remembering the syntax of window functions.

Series: 90 Days of Data Engineering Progress: 3/90 problems completed

Tags: #DEQuest #LeetCode #SQL #DataEngineering #BuildInPublic