Top 50 SQL Query Interview Questions 🚀

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Introduction

SQL (Structured Query Language) is the backbone of relational databases. Interviewers often test candidates on their ability to write queries that retrieve, filter, aggregate, and manipulate data efficiently. This blog organizes the Top 50 SQL Query Interview Questions into structured sections for easy preparation.

1. Basics

  1. What is SQL and why is it used?

  2. Difference between SQL and NoSQL databases?

  3. How do you create a table in SQL?

  4. How do you insert data into a table?

  5. How do you update records in SQL?

  6. How do you delete records in SQL?

  7. What is the difference between DELETE, TRUNCATE, and DROP?

  8. How do you use WHERE clause in SQL?

  9. What is the difference between CHAR and VARCHAR?

  10. How do you use LIKE operator in SQL?

2. Joins

  1. What is a SQL join?

  2. Difference between INNER JOIN and OUTER JOIN?

  3. What is LEFT JOIN?

  4. What is RIGHT JOIN?

  5. What is FULL OUTER JOIN?

  6. How do you perform a self join?

  7. What is CROSS JOIN?

  8. How do you join more than two tables?

  9. How do you handle NULL values in joins?

  10. What is the difference between JOIN and UNION?

3. Aggregations

  1. What are aggregate functions in SQL?

  2. How do you use COUNT, SUM, AVG, MIN, and MAX?

  3. How do you use GROUP BY clause?

  4. What is the difference between GROUP BY and ORDER BY?

  5. How do you use HAVING clause?

  6. How do you find duplicates in a table?

  7. How do you calculate the nth highest salary?

  8. How do you calculate percentage in SQL?

  9. How do you use window functions like ROW_NUMBER, RANK, and DENSE_RANK?

  10. How do you calculate running totals in SQL?

4. Subqueries

  1. What is a subquery in SQL?

  2. Difference between correlated and non-correlated subqueries?

  3. How do you use subqueries in SELECT statement?

  4. How do you use subqueries in WHERE clause?

  5. How do you use subqueries in FROM clause?

  6. How do you use subqueries with IN operator?

  7. How do you use subqueries with EXISTS operator?

  8. How do you use subqueries with ANY and ALL operators?

  9. How do you optimize subqueries?

  10. What are common pitfalls of using subqueries?

5. Advanced Scenarios

  1. How do you implement indexing in SQL?

  2. Difference between clustered and non-clustered indexes?

  3. How do you use views in SQL?

  4. How do you use stored procedures in SQL?

  5. How do you use triggers in SQL?

  6. How do you handle transactions in SQL?

  7. What is ACID property in databases?

  8. How do you handle deadlocks in SQL?

  9. How do you optimize SQL queries for performance?

  10. What are best practices for writing SQL queries in enterprise projects?

Conclusion

These 50 questions cover the breadth of SQL query knowledge expected from experienced developers and database professionals. From basics and joins to aggregations, subqueries, and advanced scenarios, this list serves as a comprehensive guide for interview preparation. By mastering these topics and practicing with real-world examples, you’ll be ready to tackle interviews confidently.

This was part of Interview Preparation With Bipin — Let’

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