Top 19 SQL Interview Questions (2026)
SQL is one of the most tested skills in data analyst, backend engineer, and business intelligence interviews. Employers use SQL questions to evaluate your ability to write efficient queries, perform joins, use aggregate functions, and reason about database schema design. Whether you're preparing for a product company or an MNC, mastering SQL interview questions is non-negotiable.
What is the difference between LIKE and equals operators in SQL?
Choosing the right operator affects query accuracy and performance. Interviewers want to ensure you don't use pattern matching when exact matches are needed.
What is the difference between DELETE and TRUNCATE commands in SQL?
Candidates need to know the performance and structural implications of removing data. Interviewers check if you understand logging, rollback capabilities, and identity reset behaviors. Choosing the wrong command can lead to unnecessary performance degradation or accidental data loss.
What is the Difference Between RDBMS and DBMS?
Understanding the evolution and capabilities of database systems is crucial for selecting the right tool. Interviewers check if you know the structural and functional differences.
What is the difference between DELETE and TRUNCATE command?
Understanding these commands is essential for database maintenance. Interviewers check if you know the performance implications and transactional differences.
What is PostgreSQL?
PostgreSQL is a standard database technology. The interviewer wants to ensure the candidate understands its features, advantages, and use cases compared to other databases. It confirms technical competency in database management.
What is the difference between the LIKE and = operators in SQL?
Developers often confuse exact matches with partial matches. This question checks if you understand when to use precise equality versus flexible pattern matching. It is fundamental for writing accurate and efficient data retrieval logic.
What is the difference between DDL, DML, and DCL in SQL?
Basic SQL classification is fundamental. Interviewers check if you can categorize commands correctly and understand their purposes.
Do you have knowledge of SQL? Can you write a query to fetch student names with 'nee' as a substring?
Data retrieval is a daily task for developers. This question tests your ability to write basic queries and use string manipulation functions. It confirms you can interact with databases to extract specific information efficiently.
Write a SQL query to fetch names containing 'nee'.
Data retrieval is a daily task for developers. This checks if you know how to filter data using wildcards and substring patterns efficiently.
Write a SQL query to find duplicate records in a table
Data manipulation is crucial for analyzing business metrics. This question checks basic SQL syntax knowledge, specifically the use of GROUP BY and HAVING clauses to identify anomalies or duplicates in datasets.
What is ER model in the DBMS?
ER models are the blueprint for databases. Interviewers assess your ability to visualize and plan data structures before implementation.
What is database normalization and why is it important?
Normalization is key to efficient database design. Interviewers check if you understand how to structure tables to minimize anomalies and maintain data consistency.
What are the ACID properties of a database and why do they matter?
ACID properties ensure data integrity during transactions, which is non-negotiable for financial applications like e-commerce. Interviewers want to confirm you understand atomicity, consistency, isolation, and durability. This shows you can design systems that prevent data loss or corruption during failures.
What is Join and what are its types in SQL?
Joins are fundamental for querying relational data. Interviewers assess your ability to retrieve complex data sets and understand inner vs outer joins.
What is a transaction and explain ACID properties?
Transactions ensure reliable data processing. Interviewers want to confirm you understand how to maintain data integrity during failures or concurrent access.
What are the different Types of Keys in Relational Model?
Keys define relationships and constraints. Interviewers assess your ability to design schemas that enforce referential integrity and uniqueness.
What are the different Types of DBMS Architecture?
Architecture impacts scalability and security. Interviewers assess your ability to design systems that separate concerns effectively.
What SQL query finds the third largest salary in an employee table?
Recruiters use this question to assess logical thinking and proficiency in database querying, specifically regarding ranking and filtering data. It checks if the candidate understands how to handle duplicates and order data correctly to find specific rank values. This is a common scenario in reporting and analytics where finding top N records is a frequent requirement.
What is PostgreSQL and what are its key features?
PostgreSQL is widely used in enterprise applications. Knowledge of it indicates database proficiency. Interviewers assess if the candidate understands its advantages over other databases like MySQL.
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