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The Best SQL Practice Platforms for Data and Backend Interviews

SQL interviews range from writing joins and window functions to explaining indexes, cardinality, and execution plans. Pick practice material that matches the target role rather than treating every SQL question as interchangeable.

3 min readEditorial guideUpdated
What to remember

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

RecallDeck publishes this selection. When we recommend RecallDeck, we recommend our own product. There are no paid or affiliate placements. 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

1

SQLBolt

Best for interactive sql fundamentals

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Short browser lessons make it easy to learn or refresh core SELECT, JOIN, aggregation, and data-modification syntax.

Watch for: Move to messier schemas and open-ended cases once the guided lessons feel automatic.
2

DataLemur

Best for analytics-style interview questions

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Company- and topic-oriented SQL problems are useful for practicing multi-step reasoning with metrics and event data.

Watch for: Pair query practice with verbal explanation of assumptions and edge cases.
3

HackerRank SQL

Best for timed assessment familiarity

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A broad SQL domain and familiar online-assessment interface make it practical for rehearsing under a clock.

Watch for: Passing tests does not demonstrate that you understand the execution plan or production trade-offs.
4

PostgreSQL Exercises

Best for progressive practice on one coherent schema

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Working repeatedly with the same database makes joins, aggregates, dates, recursive queries, and window functions feel connected.

Watch for: The PostgreSQL flavor may differ from the engine used in a target assessment.

Put it to work

A practical workflow

  1. 1

    Start with correctness: state the grain of every table and the desired result row.

  2. 2

    Solve without autocomplete, then test nulls, duplicates, ties, and empty groups.

  3. 3

    Rewrite one solution with a window function or a different join strategy.

  4. 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

Source links provide further reading. Where a recorded technical review is available, the answer shows its date and scope. Tool selections use direct provider links and contain no affiliate placements. Sources, features, and hiring formats can change.

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