SQL interviews don’t just test syntax.
They test how well you:
- Understand data relationships
- Translate business questions into logic
- Think step-by-step
Below are 24 SQL problems that companies use to evaluate real analytical thinking, not memorization.
What Interviewers Are Really Testing
With these problems, interviewers want to see if you can:
- Break vague questions into steps
- Choose the right joins and filters
- Validate results logically
If you can explain your approach, you’re already ahead.
Beginner-Level SQL Problems
1. Find the total number of customers
Tests: COUNT()
2. Find the total revenue per month
Tests: GROUP BY, date handling
3. Find customers who placed more than one order
Tests: GROUP BY, HAVING
4. Find the top 5 products by sales
Tests: ORDER BY, LIMIT
5. Find orders placed in the last 30 days
Tests: date filters
6. Find customers who never placed an order
Tests: LEFT JOIN, NULL handling
Intermediate-Level SQL Problems
7. Find average order value per customer
Tests: aggregation logic
8. Find duplicate records in a table
Tests: grouping and counting
9. Find the highest-spending customer
Tests: subqueries or ranking
10. Calculate month-over-month growth
Tests: window functions
11. Find customers who ordered in consecutive months
Tests: date logic
12. Rank products by category sales
Tests: RANK() / DENSE_RANK()
13. Find the second highest salary
Tests: subqueries or window functions
14. Identify churned customers
Tests: time-based logic
15. Compare this month’s sales to last month
Tests: self-joins or window functions
Advanced-Thinking SQL Problems
16. Find users who upgraded plans
Tests: event sequencing
17. Calculate rolling 7-day averages
Tests: window frames
18. Identify abnormal spikes in activity
Tests: trend comparison
19. Find products with declining sales
Tests: time series logic
20. Detect data inconsistencies between tables
Tests: joins and validation
21. Identify customers at risk of churn
Tests: behavioral analysis
22. Segment customers by behavior
Tests: case statements
23. Compare performance across regions
Tests: multi-level aggregation
24. Validate KPI calculations
Tests: business logic and sanity checks
How to Approach These Problems in Interviews
Before writing SQL:
- Clarify the question
- Identify tables and keys
- Decide on joins
- Define metrics
- Validate output
Interviewers care more about your thinking than perfect syntax.
If you can solve these problems:
- You understand SQL beyond basics
- You can handle real business questions
- You’re interview-ready
SQL is not about memorization, it’s about logic.
FAQs
1. Are these SQL problems good for beginners?
Yes. They start simple and gradually increase in complexity.
2. Do I need advanced SQL to solve these?
No. Strong logic matters more than advanced syntax.
3. Are these problems asked in real interviews?
Yes. Variations of these appear in many data analyst interviews.
4. Should I write full queries when practicing?
Yes. Writing and explaining queries builds confidence.
5. How often should I practice SQL problems?
Consistent practice, even 20–30 minutes daily, works best.