Top 77 MySQL / SQL Interview Questions & Answers (2026)

01 What is SQL? 02 What is a relational database? 03 What is the difference between a database and a table? 04 What is a primary key? 05 What is a foreign key? 06 What is the SELECT statement? 07 What is the WHERE clause? 08 What are SQL data types in MySQL? 09 What is INSERT, UPDATE, and DELETE in SQL? 10 What is the difference between DELETE and TRUNCATE? 11 What are SQL aggregate functions? 12 What is GROUP BY in SQL? 13 What is the ORDER BY clause? 14 What is LIMIT and OFFSET in MySQL? 15 What are SQL constraints? 16 What is NULL in SQL and how do you handle it? 17 What is the difference between CHAR and VARCHAR? 18 What is the LIKE operator in SQL? 19 What is an alias in SQL? 20 What is a JOIN in SQL? 21 What is the difference between INNER JOIN and LEFT JOIN? 22 What is a subquery in SQL? 23 What is the UNION operator in SQL? 24 What is the difference between HAVING and WHERE? 25 What is normalization in databases? 26 What is denormalization? 27 What is an index in SQL? 28 What is the difference between a clustered and non-clustered index? 29 What is a VIEW in SQL? 30 What is a stored procedure in MySQL? 31 What is a trigger in MySQL? 32 What is a transaction in SQL? 33 What are ACID properties in databases? 34 What are transaction isolation levels in MySQL? 35 What is the difference between MyISAM and InnoDB? 36 What is the AUTO_INCREMENT attribute in MySQL? 37 What is the MySQL EXPLAIN command? 38 What is the difference between UNION and UNION ALL? 39 What is a composite key?

01 What are window functions in SQL? 02 What is a CTE (Common Table Expression) in SQL? 03 What is query optimization in MySQL? 04 What is the difference between OLTP and OLAP databases? 05 What is database sharding? 06 What is a covering index in MySQL? 07 What is MySQL replication? 08 What is the difference between soft delete and hard delete? 09 What are SQL string functions? 10 What are SQL date and time functions? 11 What is the CASE expression in SQL? 12 What is the difference between optimistic and pessimistic locking? 13 What is database partitioning in MySQL? 14 What is the difference between VARCHAR and TEXT in MySQL? 15 What is query caching in MySQL? 16 What is the difference between COUNT(*), COUNT(1), and COUNT(column)? 17 What are prepared statements and why should you use them? 18 What is the MySQL binary log (binlog)? 19 What is the slow query log in MySQL? 20 What is MySQL FULLTEXT search? 21 What is the difference between DATETIME and TIMESTAMP in MySQL? 22 What is database connection pooling? 23 What are common MySQL performance tuning settings?

01 What is the difference between B-tree and Hash indexes in MySQL? 02 What is MVCC (Multi-Version Concurrency Control) in MySQL? 03 What is the InnoDB Buffer Pool and how does it work? 04 What is deadlock in MySQL and how do you prevent it? 05 What is the query execution plan and how does the MySQL optimizer work? 06 What is the difference between optimistic locking with version numbers and timestamps? 07 What are common SQL anti-patterns to avoid? 08 What is Change Data Capture (CDC) in MySQL? 09 How do you implement pagination efficiently in MySQL? 10 What is event scheduling in MySQL? 11 What is MySQL's performance schema? 12 What is ProxySQL and how does it help MySQL deployments? 13 What are generated columns in MySQL? 14 What is the difference between a function and a stored procedure in MySQL? 15 How does MySQL handle full-text indexing vs regular B-tree indexing for large text searches?