SQL Interview Questions 1-50

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SQL Interview Questions are essential for anyone preparing to enter the data and software industry. Whether you’re a beginner or an experienced developer, understanding how to confidently answer SQL-based questions can significantly boost your chances in technical interviews. In this guide, we cover the most commonly asked SQL Interview Questions with clear explanations, practical examples, and tips to help you succeed.

SQL Interview Questions 1-50

Must Know SQL Interview Questions for Guaranteed Success

  1. What is the diffrence between EXISTS and IN?
  2. How can you detect and prevent deadlock in SQL?
  3. How would you handle slowing changing dimensions in SQL?
  4. What is SQL and why is it important for data management?
  5. What is the Difference between INNER JOIN and OUTER JOIN?
  6. How do you retrive the uniqe values from a column in SQL?
  7. Explain the diffrence between WHERE and HAVING Clauses?
  8. What is the Purpose of Group by Clause in SQL?
  9. How do you Create a table in SQL ? Can you give Example?
  10. What is the Purpose of primary key in a table table?
  11. how can you delete dublicate rowsin SQL?
  12. What is a Subquery and how it is used in SQL?
  13. What is the dfference between UNION and UNION ALL?
  14. how do you find the seconds highest salary in table?
  15. What is Store procedure In SQL and why would use one?
  16. Explain the Purpose of the Count Functions in SQL?
  17. How do you Calculate the Median Salary in a department using SQL?
  18. What is dierence between correlated and non-correlated subqueries?
  19. How can you update data in ne table based on values form another?
  20. Write a windows functions and how are they different from GROUP BY?
  21. How do you find gaps in a sequesnce (like missing bill number)?
  22. how would you delete every nth row from a table?
  23. How Can youtranspose of columns into rows(unpivot) in SQL?
  24. What Purpose of the COALESCE function and how is it dffrent from ISNULL or NVL?
  25. How do you can calculate the difference in days, months or years between two days?
  26. How do you write a SQL to show cumulative percentage o salles per region?
  27. How do you rank items within partitions based on a custom sorting logic?
  28. How do you detect circular references in a hierarchical table structure?
  29. What is the difference between a clusterd and non-clustered index?
  30. How do you audit changes (INSERT/UPDATE/DELETE) in a table using SQL?
  31. What is recursive CTE and where would you use it?
  32. How do you filter the top 3 products by revenue within each category?
  33. What Strategies can you use to reduce the execution time of complex joins?
  34. What is Difference between delete and truncate command?
  35. what is the Diffence between Delete and Drop and Truncate Command?
  36. What is the Difference between Where and having Clause?
  37. What is View in SQL and how to create it?
  38. What is Data Flow Daigram and how we will create it?
  39. How to install SQL Server Can you explain it?
  40. What is trigger and how we will create and what is the use of it?
  41. What is temp table in SQL Server and what is the use of table and how we will create a temp table?
  42. What is Global temp table and how we will create a global temp table and what is the use of it?
  43. What is the difference between global temp and temp table?
  44. What is index and what is the use of it and how it will help to improve performance of query?
  45. What is Queary Optimization ?
  46. How you will performace query optimization for long or very slow running query?
  47. What is Data type in SQL and what is the use of it?
  48. What is Funcation ?
  49. Can you please write a function to check employee salary who is getting below 1000?
  50. What is RDBMS?
  51. what is normalization in sql?
  52. What is schema is SQL?

Top Tip for SQL Interview Questions to Boost Your Confidence

1.Master the Basics for SQL InterView Questions
  Understand SQL fundamentals—SELECT, INSERT, UPDATE, DELETE, WHERE, GROUP BY, ORDER BY, and JOINs. Most interviews test these heavily.
2.Practice JOINs Thoroughly for SQL InterView Questions
  INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN are common in real-world SQL questions. Be ready to explain the difference with examples.
3.  Understand Data Types & Constraints
  Know the difference between CHAR vs VARCHAR, INT vs BIGINT, and how constraints like PRIMARY KEY, FOREIGN KEY, and UNIQUE work.
4.Get Comfortable with Aggregations
  Functions like COUNT(), SUM(), AVG(), MAX(), and MIN() often appear in filtering and grouping questions.

SQL InterView Questions
5.Learn Subqueries & CTEs
  Practice writing nested queries and using Common Table Expressions (CTEs) for readability and complex data manipulation.
6.Focus on Real-Life Scenarios
  Employ real-world datasets (like banking, ecommerce, etc.) to practice solving business problems using SQL.
7.Optimize for Performance
  Know how indexes work and be ready to discuss query optimization techniques, even if just the basics.
8.Practice with Mock Tests & Platforms
  Use platforms like LeetCode, HackerRank, or Mode Analytics to practice SQL questions in an interview-like environment.
9.Explain Your Thought Process
  In interviews, verbalize your logic. Interviewers value clarity in problem-solving as much as the final answer.
10.Review Past Interview Questions
  Go through common SQL interview questions from companies like Google, Amazon, and banking institutions.

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