SQL Interview Questions

SQL shows up in interviews for backend, data engineering, data science, and full-stack roles. These questions go beyond basic SELECT statements to cover the query patterns interviewers actually test — JOINs, window functions, CTEs, and performance optimization. Each question includes the schema context, expected query, and the reasoning interviewers look for in your approach.

5 questions • 4 categories • Updated March 2026

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Fundamentals

Entry-Level 6 min

SQL JOINs Explained — INNER, LEFT, RIGHT, FULL, CROSS

Explain the different types of SQL JOINs. When would you use each one?
Entry-Level 5 min

GROUP BY and HAVING in SQL — Aggregation Interview Questions

Explain GROUP BY and HAVING. What's the difference between WHERE and HAVING?

Advanced Queries

Mid-Level 7 min

SQL Window Functions — ROW_NUMBER, RANK, LAG, and More

What are window functions? How are they different from GROUP BY? Give examples of common window functions.

Performance

Senior 8 min

SQL Query Optimization — Indexes, EXPLAIN, and Performance

How do you optimize a slow SQL query? Walk me through your approach.

Query Patterns

Mid-Level 5 min

CTEs vs Subqueries vs Temp Tables — When to Use Each

What is a CTE? How does it compare to a subquery or a temp table?