Preparing for a technical interview and want to stand out? While basic SQL gets you started, it’s the complex SQL queries for interview that truly test your data manipulation skills.
In this blog, we’ll cover 10 high-impact, real-world complex SQL queries commonly asked during interviews, especially for roles like backend developers, data analysts, and database administrators.
Let’s dive in!
🚀 Why Focus on Complex SQL Queries?
Basic queries test syntax. Complex SQL queries test your thinking, optimization, and problem-solving abilities. Companies like Infosys, TCS, Accenture, and product-based startups frequently ask layered queries involving multiple joins, subqueries, CTEs, and window functions.
🧩 Top 10 Complex SQL Queries for Interview
1. Find the second highest salary
SELECT MAX(Salary)
FROM Employees
WHERE Salary < (SELECT MAX(Salary) FROM Employees);
✅ Why it’s asked: Tests subquery logic and understanding of aggregate functions.
2. Retrieve employees who earn more than the department average
SELECT Name, Department, Salary
FROM Employees e
WHERE Salary > (
SELECT AVG(Salary)
FROM Employees
WHERE Department = e.Department
);
✅ Why it’s asked: Tests correlated subqueries.
3. List employees with duplicate salaries
SELECT Salary, COUNT(*)
FROM Employees
GROUP BY Salary
HAVING COUNT(*) > 1;
✅ Why it’s asked: Assesses GROUP BY + HAVING combo.
4. Find the nth highest salary using CTE
WITH Ranked AS (
SELECT Name, Salary, DENSE_RANK() OVER (ORDER BY Salary DESC) AS rnk
FROM Employees
)
SELECT Name, Salary FROM Ranked WHERE rnk = 3;
✅ Why it’s asked: Tests use of Common Table Expressions and window functions.
5. Retrieve departments with more than 3 employees
SELECT Department, COUNT(*) as EmpCount
FROM Employees
GROUP BY Department
HAVING COUNT(*) > 3;
✅ Why it’s asked: To test filtering after grouping.
6. Find employees who joined in the last 30 days
SELECT *
FROM Employees
WHERE JoinDate >= CURDATE() - INTERVAL 30 DAY;
✅ Why it’s asked: Real-world use of date functions.
7. Self-join to find managers and their subordinates
SELECT A.Name AS Manager, B.Name AS Employee
FROM Employees A
JOIN Employees B
ON A.ID = B.ManagerID;
✅ Why it’s asked: Evaluates understanding of self-joins and data relationships.
8. List departments with average salary above total average
SELECT Department
FROM Employees
GROUP BY Department
HAVING AVG(Salary) > (SELECT AVG(Salary) FROM Employees);
✅ Why it’s asked: Another layer of correlated logic.
9. Get top 2 earners from each department
SELECT Name, Department, Salary
FROM (
SELECT Name, Department, Salary,
RANK() OVER (PARTITION BY Department ORDER BY Salary DESC) AS rnk
FROM Employees
) ranked_employees
WHERE rnk <= 2;
✅ Why it’s asked: Window functions + partitioning logic.
10. Find employees who never had a project
SELECT Name
FROM Employees
WHERE ID NOT IN (SELECT EmployeeID FROM Projects);
✅ Why it’s asked: To test anti-joins using NOT IN or LEFT JOIN IS NULL.
🎯 Interview Tips for Complex SQL Queries
- Break down the problem step-by-step before writing the full query.
- Think of data as relationships – joins are your best friend.
- Practice scenarios from job platforms like HackerRank, LeetCode, and InterviewBit.
❓ FAQs – Complex SQL Queries for Interview
Q1: Do I need to memorize these queries?
Not at all. Focus on the patterns. Understand what each query does and try building variations.
Q2: Are these queries useful for Data Analyst roles?
Absolutely! Analysts deal with aggregated, filtered, and joined datasets every day.
Q3: What’s the best platform to practice complex SQL?
Try:
- LeetCode – Database section
- Mode Analytics SQL tutorials
- HackerRank – Advanced SQL challenges
🧠 Final Thoughts
Mastering complex SQL queries for interview not only boosts your confidence but also makes you stand out from other candidates. The more you practice, the more intuitive these patterns become.
💡 Tip: Try rewriting the same logic using different methods (CTEs vs. subqueries vs. joins) to strengthen your skillset.