When preparing for interviews, most candidates expect questions like “What is a primary key?” or “Explain normalization.” But the reality is different. Interviewers often ask tricky, real-world problems to test not just your memory but your problem-solving ability.
These database interview questions can look simple on the surface but require a deeper understanding of SQL, indexing, joins, and optimization. In this blog, we’ll explore some of the most common tricky questions and their solutions, along with explanations to help you master them.
The goal isn’t to confuse you—it’s to see if you:
Can apply SQL concepts in practical scenarios.
Understand performance trade-offs (speed, storage, scalability).
Know how to debug and optimize queries.
Communicate your logic clearly, not just write code.
That’s why tricky database interview questions are a favorite among hiring managers.
Let’s break down ten frequently asked tricky questions with examples and answers.
DELETE: Removes rows (one by one), can use WHERE. Slower but safer.
TRUNCATE: Quickly clears all rows, resets identity columns. Cannot filter rows.
DROP: Removes the entire table and structure.
Why it’s tricky: Many assume DELETE and TRUNCATE are the same.
SELECT DISTINCT salary
FROM Employees
ORDER BY salary DESC
LIMIT 1 OFFSET 1;
Alternate solution:
SELECT MAX(salary)
FROM Employees
WHERE salary < (SELECT MAX(salary) FROM Employees);
Why it’s tricky: Different SQL engines require different techniques.
UNION: Combines results, removes duplicates (slower).
UNION ALL: Combines results, keeps duplicates (faster).
Why it’s tricky: Candidates forget about performance implications.
SELECT column_name, COUNT(*)
FROM TableName
GROUP BY column_name
HAVING COUNT(*) > 1;
Why it’s tricky: Using DISTINCT won’t always reveal duplicates correctly.
Clustered Index: Determines the physical order of rows. One per table.
Non-Clustered Index: Separate structure, multiple allowed, points to rows.
Why it’s tricky: Many confuse index types and don’t explain performance trade-offs.
SELECT employee_id, name, department_id, salary
FROM (
SELECT employee_id, name, department_id, salary,
RANK() OVER (PARTITION BY department_id ORDER BY salary DESC) AS rnk
FROM Employees
) ranked
WHERE rnk <= 3;
Why it’s tricky: Tests knowledge of window functions.
WHERE: Filters rows before grouping.
HAVING: Filters after aggregation (can use SUM, COUNT).
Why it’s tricky: Many don’t understand SQL execution order.
SELECT o1.order_id + 1 AS missing_id
FROM Orders o1
WHERE NOT EXISTS (
SELECT 1 FROM Orders o2 WHERE o2.order_id = o1.order_id + 1
)
ORDER BY missing_id;
Why it’s tricky: Real-world task for tracking missing invoices or transactions.
No. A table can only have one primary key, though it may include multiple columns (composite key).
Why it’s tricky: Many confuse primary keys with unique constraints.
INNER JOIN: Only matching rows.
LEFT JOIN: All left rows + matching right rows.
RIGHT JOIN: All right rows + matching left rows.
FULL JOIN: All rows when a match exists in either.
Why it’s tricky: LEFT and RIGHT joins often confuse beginners.
Clarify first – Restate the requirement before writing SQL.
Start with simple logic – Then optimize if needed.
Think scalability – Will your query work on millions of rows?
Explain trade-offs – Show awareness of indexes, joins, and design choices.
Practice scenarios – Use sample databases to get hands-on experience.
Tricky database interview questions aren’t just about theory—they’re designed to test how you approach real-world problems. From handling duplicates to ranking employees, from understanding indexes to optimizing queries, each question evaluates both your technical knowledge and your problem-solving ability.
The secret to cracking them? Don’t just memorize answers. Understand the logic behind each solution, practice with real datasets, and be ready to explain your reasoning clearly. That way, even the trickiest questions will become your chance to stand out.