DBMS Interview Questions (Product + Service Companies)

These are grouped into categories, with brief explanations to help students understand what each type of company expects and how to prepare.

1. Conceptual & Theoretical Questions (Common in Both)

These test a solid understanding of DBMS fundamentals.

• What is normalization? Explain different normal forms.
• What are ACID properties in a transaction?
• What is the difference between a clustered and non-clustered index?
• What are functional, multivalued, and transitive dependencies?
• What are the different types of joins? Give examples.
• What is the difference between DELETE, TRUNCATE, and DROP?
• Explain primary key vs. unique key.
• What is a view? How does it differ from a table?

2. SQL Coding Questions (Common in Product Companies, Some Service Roles)

Product companies often test SQL coding via online assessments.

• Write a query to get the second highest salary from an employee table.
• Write a query to get customers who never placed an order.
• Write an SQL query to find duplicate records in a table.
• Given a sales table, write a query to find the top 3 products sold each month.
• Use window functions to rank employees based on salary within departments.

3. Design-Oriented Questions (Mostly Product-Based & Project Roles)

These assess ability to design efficient databases and understand trade-offs.

• Design a database schema for a food delivery app (like Swiggy or Zomato).
• How would you handle schema changes in a live production database?
• What strategies would you use to scale a DB as data grows?
• Explain indexing strategies for optimizing read-heavy systems.
• Discuss the pros and cons of SQL vs NoSQL for a messaging system.

4. Transactions & Concurrency Control (Important for Backend/System Roles)

Crucial for understanding consistency in multi-user environments.

• What are different transaction states in DBMS?
• Explain conflict vs. view serializability with examples.
• What is Two-Phase Locking (2PL)? What problem does it solve?
• What is deadlock? How do you detect and resolve it?
• Explain the difference between strict, cascadeless, and recoverable schedules.

5. Recovery & Logging (Advanced, Appears in Systems/Backend Roles)

• What is log-based recovery in DBMS?
• Explain the concept of checkpoints in crash recovery.
• What is shadow paging and how does it work?
• Compare deferred update and immediate update techniques.

6. Distributed Databases & NoSQL (Useful for Projects & Scalable System Interviews)

• What is the CAP theorem?
• Compare replication vs sharding.
• What is BASE in NoSQL systems?
• When would you choose MongoDB over MySQL?
• How do distributed transactions maintain consistency?