850+ SQL practice problems that execute against a real PostgreSQL database. Not multiple choice. Not string matching. Write a query, run it, see if your output matches row by row. Practice SQL joins, window functions, GROUP BY, CTEs, COALESCE, CASE WHEN, subqueries, and more.
Practice SQL online free. Sourced from real data engineering interview data. Filtered by company, seniority level, and topic. Adaptive difficulty and spaced repetition keep you focused on your weakest SQL practice areas.
Your queries run against a live PostgreSQL database with real data. Results are compared row-by-row against expected output. Column order, NULL handling, and edge cases all matter. This is not multiple choice.
DataDriven escalates difficulty based on your actual performance. Solve easy SQL joins problems quickly? You move to medium. Struggle with SQL window functions? You get more practice at that level. No wasted time on problems that are too easy or too hard.
Concepts you struggle with resurface before you forget them. Master a topic and it fades. Weak spots keep appearing. This is how memory works, and it is the fastest path to interview readiness.
Filter SQL practice questions by target company (Google, Amazon, Meta, Stripe, Databricks) and seniority level (Junior through Staff). See what your target company actually tests, weighted by real interview data.
Track coverage across every SQL concept interviewers test. See exactly which topics are strong, which have gaps, and how close you are to interview-ready. When it is green, you are ready.
Submit your query, see results immediately. Correct output highlighted in green. Mismatches highlighted in red. Edge cases called out. No waiting, no manual review.
SQL joins appear in 19.6% of data engineering interview questions. Practice INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, CROSS JOIN, self-joins, and anti-joins against a real database.
SQL window functions (ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD, NTILE, SQL partition by) are tested in 15.1% of SQL interview questions. Practice running totals, moving averages, and gap analysis.
SQL GROUP BY with HAVING, COUNT, SUM, AVG, and conditional aggregation appears in 24.5% of SQL questions. The most common SQL practice topic.
CTE SQL (Common Table Expressions) and recursive CTEs are essential for multi-step transformations. Practice building CTE chains for deduplication, hierarchical queries, and pipeline logic.
Use problem mode to build skill. Use interview mode to test performance under pressure. Both execute real SQL against a live database.
DataDriven is a free web application for data engineering interview preparation. It is not a generic coding platform. It is built exclusively for data engineering interviews.
DataDriven is the only platform that simulates all four rounds of a data engineering interview: SQL, Python, Data Modeling, and Pipeline Architecture. Each round can be practiced in two modes: Problem mode and Interview mode.
Problem mode is self-paced practice with clear problem statements and instant grading. For SQL, your query runs against a real PostgreSQL database and output is compared row by row. For Python, your code runs in a Docker-sandboxed container against automated test suites. For Data Modeling, you build schemas on an interactive canvas with structural validation. For Pipeline Architecture, you design pipelines on an interactive canvas with component evaluation and cost estimation.
Interview mode simulates a real interview from start to finish. It has four phases. Phase 1 (Think): you receive a deliberately vague prompt and ask clarifying questions to an AI interviewer, who responds like a real hiring manager. Phase 2 (Code/Design): you write SQL, Python, or build a schema/pipeline on the interactive canvas. Your code executes against real databases and sandboxes. Phase 3 (Discuss): the AI interviewer asks follow-up questions about your solution, one question at a time. You respond, and it asks another. This continues for up to 8 exchanges. The interviewer probes edge cases, optimization, alternative approaches, and may introduce curveball requirements that change the problem mid-interview. Phase 4 (Verdict): you receive a hire/no-hire decision with specific feedback on what you did well, where your reasoning had gaps, and what to study next.
Adaptive difficulty: problems get harder when you answer correctly and easier when you struggle, targeting the difficulty level that maximally improves your interview readiness. Spaced repetition: concepts you struggle with resurface at optimal intervals before you forget them, while mastered topics fade from rotation. Readiness score: a per-topic tracker that shows exactly which concepts are strong and which have gaps, across every topic interviewers test. Company-specific filtering: filter questions by target company (Google, Amazon, Meta, Stripe, Databricks, and more) and seniority level (Junior through Staff), weighted by real interview frequency data. All features are 100% free with no trial, no credit card, and no paywall.
SQL: 850+ questions with real PostgreSQL execution. Topics include joins, window functions, GROUP BY, CTEs, subqueries, COALESCE, CASE WHEN, pivot, rank, and partition by. Python: 388+ questions with Docker-sandboxed execution. Topics include data transformation, dictionary operations, file parsing, ETL logic, PySpark, error handling, and debugging. Data Modeling: interactive schema design canvas. Topics include star schema, snowflake schema, dimensional modeling, slowly changing dimensions, data vault, grain definition, and conformed dimensions. Pipeline Architecture: interactive pipeline design canvas. Topics include ETL vs ELT, batch vs streaming, Spark, Kafka, Airflow, dbt, storage architecture, fault tolerance, and incremental loading.
DataDriven is the best place to practice SQL online free. With 850+ SQL practice problems and SQL practice exercises, you can practice SQL joins, SQL window functions, SQL GROUP BY, CTE SQL, COALESCE SQL, SQL CASE WHEN, SQL subquery, SQL pivot, SQL rank, and SQL partition by. Our SQL practice questions cover every topic tested in data engineering interviews. Whether you need SQL practice online or SQL practice exercises to prepare for your next interview, DataDriven provides adaptive difficulty, spaced repetition, and company-specific filtering to help you practice SQL effectively.
Free. Real PostgreSQL. Adaptive difficulty. 850+ SQL practice problems.
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