Write a SQL query to find the nth highest salary in a table.

Official Answer

Certainly, I appreciate the opportunity to discuss my approach to solving SQL queries, particularly ones that require a bit of creative thinking like finding the nth highest salary in an 'employees' table. Let's dive into how I would tackle this question, which I believe showcases not only my technical proficiency but also my ability to approach problems logically and efficiently.

First, let's clarify the task: we need to write an SQL query that returns the nth highest salary from an 'employees' table that includes a 'salary' column. It's essential to handle cases where there might be duplicate salaries, ensuring that the nth highest is accurately identified even when multiple employees share the same salary figures.

WITH SalaryRanks AS (
  SELECT salary,
         DENSE_RANK() OVER (ORDER BY salary DESC) AS rank
  FROM employees
)
SELECT salary
FROM SalaryRanks
WHERE rank = @n;

In this solution, I've used a Common Table Expression (CTE) named SalaryRanks for clarity and maintainability. Within this CTE, I employ the DENSE_RANK() function to assign a unique rank to each distinct salary, ordered in descending order to ensure that the highest salary receives a rank of 1. By using DENSE_RANK(), we effectively deal with duplicate salaries by assigning them the same rank, which is crucial for accurately identifying the nth highest salary.

The @n in the WHERE clause represents the nth highest salary we're interested in finding. This parameter would be substituted with the specific rank we're looking for in a given query execution.

Let me briefly explain why I chose DENSE_RANK() over other ranking functions. Unlike RANK(), which could leave gaps in the ranking sequence when encountering duplicates, DENSE_RANK() keeps the sequence contiguous, which is vital for our use case. ROW_NUMBER(), another alternative, would not handle duplicates as we'd like for this scenario because it would assign a unique row number to each row, regardless of duplicate salary values, which could lead to incorrect results for our specific need.

What makes this approach versatile is its adaptability. Candidates can easily modify the @n parameter to find not just the nth highest salary but also to explore other ranking queries within the same framework. It showcases an understanding of SQL's powerful window functions and provides a robust solution to a common yet complex query task, reflecting a candidate's readiness to tackle real-world database problems.

In conclusion, this solution not only highlights my technical skills in SQL but also demonstrates a strategic approach to problem-solving, ensuring accuracy, efficiency, and adaptability. These are critical qualities I've honed over my career and are essential for success in roles that require precision and creativity in data management and analysis.