SQL Interview Preparation for Beginners

Whether this is your first SQL interview or your fifth, the questions come from the same short list of topics. This collection is a complete, ordered path through them for freshers (0 to 1 year of experience): learn a topic, practise it with a short query, then test yourself.

How the path is organised

1. Start here (step 1): the 30-day roadmap and a small practice database.
2. Foundations (steps 2 to 4): keys and constraints, , and , then the SQL Basics quiz.
3. Aggregates and joins (steps 5 to 9): , joins, finding duplicates, self joins, and the joins quiz.
4. Subqueries and window functions (steps 10 to 17): , CTEs, ranking, "Nth highest salary", removing duplicates and running totals, with a quiz.
5. Indexes, design and transactions (steps 18 to 23): performance, normalization and ACID, with a second quiz.
6. Interview readiness (steps 24 and 25): the 20 mistakes to avoid and the 50 most-asked questions with short answers.

The examples target Microsoft SQL Server (T-SQL) and mostly run unchanged on PostgreSQL and MySQL. Differences are called out as you go.

Each step also has its own page, so you can jump straight to the topic you need.