If you're preparing for a career in data analytics, database management, or backend development, one skill you absolutely must master is SQL (Structured Query Language). Whether you're a fresher or someone looking to transition into tech, understanding the most frequently asked SQL interview questions can give you a significant edge.

✅ Top SQL Interview Questions & Answers

1. What is SQL?
   SQL stands for Structured Query Language. It's used for storing, manipulating, and retrieving data in relational databases.
2. What are the different types of SQL commands?

• DDL – Data Definition Language (CREATE, ALTER, DROP)
• DML – Data Manipulation Language (INSERT, UPDATE, DELETE)
• DCL – Data Control Language (GRANT, REVOKE)
• TCL – Transaction Control Language (COMMIT, ROLLBACK)

3. What is the difference between WHERE and HAVING?

• WHERE filters rows before grouping.
• HAVING filters groups after aggregation.

4. Explain different types of JOINs.

• INNER JOIN: Returns matching rows from both tables.
• LEFT JOIN: Returns all rows from the left table, even if there’s no match.
• RIGHT JOIN: Returns all rows from the right table.
• FULL OUTER JOIN: Returns all rows when there is a match in either table.

5. What is Normalization?
   Normalization is the process of organizing data to reduce redundancy and improve data integrity. Common forms include 1NF, 2NF, and 3NF.
6. What is a Subquery?
   A subquery is a query nested inside another query. It can be used in SELECT, INSERT, UPDATE, or DELETE statements.
7. What is the difference between DELETE and TRUNCATE?

• DELETE removes rows based on a condition and can be rolled back.
• TRUNCATE removes all rows and is faster but cannot be rolled back.

Read More : SQL Fresher Interview Questions

8. What are indexes?
   Indexes improve the speed of data retrieval operations. However, they can slow down data modification operations.

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