Java Interview Preparation
Database Interview Questions
SQL, NoSQL, indexes, normalization, transactions, and database performance.
Database Interview Focus
SQL, NoSQL, indexes, normalization, transactions, and database performance.
Interview questions
1. What is the difference between SQL and NoSQL databases? Beginner
2. What is the difference between a primary key and a unique key? Beginner
3. What is the difference between a primary key and a foreign key? Beginner
4. What is database normalization, and why is it required? Beginner
5. What are First, Second, and Third Normal Forms? Intermediate
6. What is denormalization, and when should it be used? Intermediate
7. What are joins, and what are the different types of SQL joins? Beginner
8. What is the difference between INNER JOIN, LEFT JOIN, and FULL OUTER JOIN? Beginner
9. What is the difference between WHERE and HAVING? Beginner
10. What is the difference between GROUP BY and ORDER BY? Beginner
11. What is the difference between a subquery and a join? Intermediate
12. What is an index, and how does it improve query performance? Beginner
13. What is the difference between clustered and non-clustered indexes? Intermediate
14. What is a composite index, and why does column order matter? Advanced
15. What are ACID properties in database transactions? Beginner
16. What are transaction isolation levels? Intermediate
17. What are dirty reads, non-repeatable reads, and phantom reads? Advanced
18. What is a database deadlock, and how can it be prevented? Advanced
19. How does database connection pooling work in a Java application? Intermediate
20. How do you identify and optimize a slow SQL query? Advanced
How to Prepare for Java Technical Interviews
Use this Java technical interview question bank to revise core concepts and practise explaining your decisions clearly. The questions cover Java fundamentals, object-oriented programming, collections, exceptions, multithreading, Spring Boot, Hibernate, databases, and other topics used in real software development interviews.
Start with the fundamentals, then move to scenario-based questions and advanced topics. Filter questions by difficulty to build confidence gradually. A strong answer should define the concept, explain why it matters, and include a practical example when appropriate.
Continue your preparation with the Java tutorials, or explore all interview preparation tracks for managerial and company-focused questions.