Top 30 SQL Interview Questions and Answers (2026)

In 2026, SQL continues to be one of the most reliable indicators of a candidate’s problem-solving and data-handling skills. Despite the rapid adoption of NoSQL databases, cloud-native platforms, and AI-driven analytics, SQL interview questions remain a non-negotiable part of technical hiring—especially for entry-level roles.

For freshers, SQL interviews often present a unique challenge. Many candidates are familiar with basic syntax, yet interviews demand more than memorization. Recruiters assess how well you understand relational thinking, data integrity, and query logic under real-world constraints.

This editorial guide is designed for freshers preparing for SQL interviews in 2026. It covers the top 30 core SQL interview questions and answers, explained with clarity and practical context. The focus is not just on what the correct answer is, but why it matters—helping you approach interviews with confidence, structure, and a strong conceptual foundation.

Overview: Understanding SQL Interview Expectations

For freshers, these SQL interview questions are designed to test conceptual clarity, relational thinking, and the ability to explain query logic clearly during interviews.SQL (Structured Query Language) is the backbone of relational database systems such as MySQL, PostgreSQL, Oracle, and SQL Server. Interviewers rely on SQL questions to evaluate how candidates think about data, relationships, and constraints—not just how they write queries.

For freshers, interviewers typically focus on:

• Fundamental SQL concepts and terminology
• Logical correctness of queries
• Understanding of tables, keys, and relationships
• Ability to explain queries clearly

You are not expected to be an optimization expert. However, a strong grasp of core SQL concepts can clearly distinguish you from other entry-level candidates.These SQL interview questions are designed to test both conceptual understanding and practical query logic, especially for fresher-level roles.

Core Concepts Explained

Before diving into questions, it is important to understand what “core SQL” means in an interview context.

Core SQL revolves around:

• Retrieving data using SELECT
• Filtering and sorting results
• Grouping and aggregation
• Joining multiple tables
• Ensuring data integrity through keys and constraints

Interviewers value simplicity, accuracy, and explanation. Clear reasoning often matters more than writing complex queries.Most fresher-level SQL interview questions are built around these core concepts. Interviewers are less concerned with advanced syntax and more focused on how well candidates understand data relationships, constraints, and logical query flow.

Top 50 Core SQL Interview Questions and Answers

The following SQL interview questions and answers reflect the most commonly tested patterns in fresher technical interviews across service-based and product-based companies.

1. What is SQL?

SQL is a language used to manage and manipulate data in relational databases. It enables users to store, retrieve, and update information efficiently. SQL works with structured data organized in tables, making it easy to query and analyze.

2. What are the different types of SQL commands?

SQL commands are categorized into:

• DDL (Data Definition Language): Commands like CREATE, ALTER, and DROP used to define or modify database structures such as tables and schemas.
• DML (Data Manipulation Language): Commands like INSERT, UPDATE, and DELETE used to manage and manipulate data within tables.
• DQL (Data Query Language): The SELECT command used to retrieve data from one or more tables.
• DCL (Data Control Language): Commands like GRANT and REVOKE used to control access and permissions for users.
• TCL (Transaction Control Language): Commands like COMMIT and ROLLBACK used to manage transactions and ensure data integrity.

3. What is a primary key?

A primary key uniquely identifies each record in a table. It must contain unique values and cannot be NULL, ensuring entity integrity.

4. What is a foreign key?

A foreign key is a column in one table that links to the primary key of another table. It helps establish a relationship between the two tables and ensures that the data remains consistent across them. This prevents invalid or orphaned records in the database.

5. What is the difference between WHERE and HAVING?

6. What are aggregate functions?

Aggregate functions are specialized SQL functions that process a set of rows and produce a single summarized value. They are commonly used in reporting and data analysis to calculate totals, averages, minimums, maximums, or counts across a dataset. Examples include COUNT, which counts rows; SUM, which adds numeric values; AVG, which calculates the average; MIN and MAX, which find the smallest and largest values respectively. These functions are often combined with GROUP BY to aggregate data by specific categories.

7. What is GROUP BY?

GROUP BY groups rows with the same values so aggregate functions can be applied to each group.

8. What is a JOIN?

A JOIN is used to retrieve data from two or more tables by linking them through a common column. It helps combine related information, making it easier to analyze and report on data that is spread across multiple tables. Different types of JOINs determine which rows are included in the result.

9. What are the types of JOINs?

• INNER JOIN: Returns only the rows that have matching values in both tables.
  Example:
  SELECT *
  FROM Employees
  INNER JOIN Departments
  ON Employees.DeptID = Departments.ID;
• LEFT JOIN: Returns all rows from the left table and the matched rows from the right table. If no match, NULLs are returned for the right table.
  Example:
  SELECT *
  FROM Employees LEFT JOIN Departments
  ON Employees.DeptID = Departments.ID;
• RIGHT JOIN: Returns all rows from the right table and the matched rows from the left table. If no match, NULLs are returned for the left table.
  Example:
  SELECT *
  FROM Employees
  RIGHT JOIN Departments
  ON Employees.DeptID = Departments.ID;
• FULL OUTER JOIN: Returns all rows when there is a match in either left or right table. Non-matching rows will have NULLs for the missing side.
  Example:
  SELECT *
  FROM Employees
  FULL OUTER JOIN Departments
  ON Employees.DeptID = Departments.ID;

10. Difference between INNER JOIN and LEFT JOIN?

INNER JOIN retrieves only the rows that have matching values in both tables. LEFT JOIN returns all rows from the left table and includes matching rows from the right table, filling with NULLs when there is no match. This allows LEFT JOIN to preserve all data from the left table even if the right table has missing matches.

11. What is a subquery?

A subquery is a query nested inside another query. It is used to retrieve data that will be used by the main query.

11. What is a nested query in SQL?

A nested query, also known as a subquery, is a query placed inside another SQL query. It allows you to use the result of one query as input for another, enabling more complex data retrieval.

13. What is NULL?

NULL represents missing or unknown data. It is not the same as zero or an empty string.

14. What is normalization?

Normalization is the process of organizing data to reduce redundancy and improve data integrity.

15. What is denormalization?

Denormalization intentionally introduces redundancy to improve read performance in certain use cases.

16. How do you find the second highest salary from a table?

You can use a subquery or window function. Example:

SELECT MAX(salary) 
FROM employees 
WHERE salary < (SELECT MAX(salary) FROM employees);

17. How do you retrieve duplicate records from a table?

SELECT column_name, COUNT(*) 
FROM table_name 
GROUP BY column_name 
HAVING COUNT(*) > 1;

18. How do you delete duplicate rows from a table?

DELETE t1 
FROM table_name t1
INNER JOIN table_name t2 
WHERE t1.id > t2.id AND t1.column_name = t2.column_name;

19. How do you find employees who joined in the last 30 days?

SELECT * 
FROM employees 
WHERE join_date >= CURRENT_DATE - INTERVAL '30 days';

20. How do you get the top N records from a table?

SELECT * 
FROM employees 
ORDER BY salary DESC 
LIMIT 5;

21. How do you find the total number of employees in each department?

SELECT department_id, COUNT(*) 
FROM employees 
GROUP BY department_id;

22. How do you update a column based on another column?

UPDATE employees 
SET bonus = salary * 0.1 
WHERE department_id = 10;

23. How do you find employees with no manager?

SELECT * 
FROM employees 
WHERE manager_id IS NULL;

24. How do you find the nth highest salary?

SELECT DISTINCT salary 
FROM employees 
ORDER BY salary DESC 
LIMIT 1 OFFSET n-1;

25. How do you find employees whose names start with ‘A’?

SELECT * 
FROM employees 
WHERE name LIKE 'A%';

26. How do you count the number of employees in each department with salary > 50000?

SELECT department_id, COUNT(*) 
FROM employees 
WHERE salary > 50000 
GROUP BY department_id;

27. How do you find employees who earn more than their manager?

SELECT e1.name 
FROM employees e1
JOIN employees e2 ON e1.manager_id = e2.id
WHERE e1.salary > e2.salary;

28. How do you find the second most recent order?

SELECT * 
FROM orders 
ORDER BY order_date DESC 
LIMIT 1 OFFSET 1;

29. How do you find employees with salaries between 40000 and 60000?

SELECT * 
FROM employees 
WHERE salary BETWEEN 40000 AND 60000;

30. How do you find employees not in a specific department?

SELECT * 
FROM employees 
WHERE department_id NOT IN (10, 20);

SQL Trends and Interview Focus in 2026

In 2026, SQL interviews increasingly emphasize:

• Real-world query logic over theory
• Understanding cloud-based relational databases
• Awareness of security fundamentals
• Clear explanation of query behavior

Freshers who combine conceptual clarity with practical thinking are more likely to succeed.

Common Mistakes Freshers Make in SQL Interviews

• Memorizing syntax without understanding logic
• Confusing WHERE and HAVING clauses
• Ignoring NULL behavior
• Over-complicating simple queries
• Failing to explain answers clearly

Avoiding these mistakes can significantly improve interview performance.

Expert Tips and Best Practices

• Focus on explaining your thought process
• Practice writing queries on sample datasets
• Revise core concepts regularly
• Learn to read and interpret existing queries
• Prioritize correctness over cleverness

Consistency and clarity matter more than speed in interviews.Practicing real-world SQL interview questions regularly helps candidates explain not just syntax, but also reasoning during interviews.

Complete Your Interview Preparation

While mastering OOPs Interview Questions and Answers builds a strong conceptual foundation, cracking real interviews requires combining OOPs with programming and database skills.

To prepare holistically for fresher interviews in 2026, continue with:

• Java Interview Questions and Answers – Ideal for service-based and product-based company interviews.
• Python Interview Questions and Answers – Perfect for scripting, backend, and automation roles.
• OOPs Interview Questions and Answers – Fundamental for mastering object-oriented design, problem modeling, and technical interview evaluations.
• System Design Interview Questions and Answers – Essential for understanding scalability, performance, databases, APIs, caching, load balancing, and designing real-world applications asked in modern technical interviews.

Conclusion

SQL remains a foundational skill for technical roles in 2026, and strong performance in SQL interviews can open doors for freshers across industries. By mastering these top 30 core SQL interview questions and answers, you build not only technical competence but also confidence in your problem-solving approach.

Rather than treating SQL as a checklist of commands, approach it as a way of thinking about data relationships and logic. Regular practice, clear explanations, and conceptual understanding will set you apart in interviews. As hiring processes continue to evolve, candidates with strong SQL fundamentals will remain in high demand—making this preparation both timely and valuable.

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