Write queries against real schemas, predict the result before running them, and explain how the database might execute the expensive parts.
Method
How we chose
This is an editorial selection, not an affiliate ranking. Tools earn a place by solving a distinct part of the target interview workflow; order is not a universal score.
- Quality and variety of schemas instead of isolated syntax puzzles
- Coverage of analytics, backend, and optimization interview styles
- Immediate feedback with enough explanation to diagnose the mistake
- A useful progression from fundamentals to multi-step business questions
Recommendations
The shortlist
SQLBolt
Best for interactive sql fundamentals
Short browser lessons make it easy to learn or refresh core SELECT, JOIN, aggregation, and data-modification syntax.
DataLemur
Best for analytics-style interview questions
Company- and topic-oriented SQL problems are useful for practicing multi-step reasoning with metrics and event data.
HackerRank SQL
Best for timed assessment familiarity
A broad SQL domain and familiar online-assessment interface make it practical for rehearsing under a clock.
PostgreSQL Exercises
Best for progressive practice on one coherent schema
Working repeatedly with the same database makes joins, aggregates, dates, recursive queries, and window functions feel connected.
Put it to work
A practical workflow
- 1
Start with correctness: state the grain of every table and the desired result row.
- 2
Solve without autocomplete, then test nulls, duplicates, ties, and empty groups.
- 3
Rewrite one solution with a window function or a different join strategy.
- 4
For backend roles, inspect an EXPLAIN plan and discuss the index you would test.
Quick answers
Frequently asked questions
Where can I practice SQL interview questions for free?
SQLBolt, HackerRank’s SQL domain, and PostgreSQL Exercises all provide substantial free practice. Choose based on whether you need guided syntax, assessment drills, or deeper schema work.
What SQL topics are most important for interviews?
Prioritize joins, aggregation, subqueries and CTEs, window functions, null behavior, deduplication, and date logic. Backend roles should add indexes, transactions, and query plans.
Source notes
References and review policy
RecallDeck’s interview answers are editorial material, reviewed against maintained official documentation where a primary reference is available. Tool selections use direct provider links and contain no affiliate placements. Features can change after the review date.
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