SQL Interview/Exam Questions With Details Explanation : 2025

About this course

Are you preparing for an SQL interview? This extensive SQL practice test, featuring 320+ SQL exam questions, is designed to help you improve your database skills, build confidence, and master SQL concepts. Whether you're a beginner or an experienced professional, this SQL certification practice test will help you prepare for real-world SQL challenges. It includes SQL multiple choice questions (MCQs) and in-depth explanations to guide you through every concept and help you strengthen your SQL query practice questions.What Topics Will We Cover in This Practice Test?Basic SQL Querieso What are the different types of SQL statements?o How do you retrieve unique values from a table?o What is the difference between WHERE and HAVING?o Explain the difference between COUNT(*), COUNT(column), and COUNT(DISTINCT column).Joins and Relationshipso Explain different types of joins (INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN, CROSS JOIN).o How do you perform a self-join?o What is the difference between JOIN and UNION?Subqueries and Common Table Expressions (CTEs)o What is a subquery? Provide an example.o What is the difference between a correlated and non-correlated subquery?o When should you use CTEs instead of subqueries?Aggregation and Groupingo How does GROUP BY work? Give an example.o What is the difference between GROUP BY and PARTITION BY?o How do you find the second highest salary in an employee table?Indexes and Performance Optimizationo What are indexes? How do they improve performance?o What is the difference between a clustered and non-clustered index?o What are some ways to optimize a slow query?Constraints and Data Integrityo What are primary and foreign keys?o What is the difference between UNIQUE and PRIMARY KEY?o How do CHECK and DEFAULT constraints work?Transactions and Concurrency Control