SQL Query Reasoning vs Quarry

SQL Query Reasoning is an independent study app for building confidence with database logic, query interpretation, and result prediction. It is designed for learners, interview candidates, analysts, developers, and anyone who wants structured practice without needing an account. Work through 160 questions across Fundamentals, Practical Skills, Common Pitfalls, and Advanced Concepts. Every question includes an explanation so you can understand why an answer is correct and where your reasoning went off track. Features: - FSRS spaced-repetition intervals for smarter review - Weak-point heatmap to spot topics that need attention - Daily challenge for consistent practice - Mock exams for timed review sessions - Offline practice for commutes and focused study - No login required Practice offline, no login required. Independent study app for SQL Query Reasoning practice. Not affiliated with, endorsed by, or sponsored by any company, certification body, exam operator, or vendor. All trademarks belong to their respective owners.

Data interview practice that runs entirely on your device. Write real SQL and Python (pandas), get graded instantly, and see exactly why. NEW IN 1.2 • Today's problem: one problem a day, on Home and in a new widget for your Home Screen and Lock Screen. • Streaks and a daily goal: solve something every day and watch the streak grow. • An optional daily reminder, off unless you turn it on. • 20 new problems: A/B tests, attribution, quartiles, pivots, rate limiters and more. • Make it yours: six accent colours and four code editor colour schemes. • Quarry Pro: every Medium and Hard problem, a review queue that brings back the problems you found hard, and every future problem pack. WHAT'S INSIDE • 188 problems across three tracks: SQL, pandas and Python (algorithms and data structures). • Real execution, real grading. Your output is checked against the expected result, with no self-marking. • Company-style practice. Filter problems written in the style of the company you're interviewing at. • Hints and full solutions when you're stuck. • Difficulty levels from Easy to Hard, grouped by topic. • A free-form Playground for scratch SQL and Python. • Designed for iPhone, iPad and iPhone Duo. FREE AND PRO Every Easy problem, a sample of Medium ones, the daily problem, streaks, the widget and the Playground are free. Quarry Pro unlocks the other 119 problems, the review queue and every future pack. Quarry Pro is available monthly or yearly (auto-renewing), or as a one-time lifetime purchase. Payment is charged to your Apple Account. Subscriptions renew automatically unless cancelled at least 24 hours before the end of the current period; manage or cancel them in your Apple Account settings. PRIVATE BY DESIGN No accounts. No analytics. No ads. No tracking. Quarry collects nothing and works fully offline. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://mayankgulaty.github.io/quarry-site/privacy.html Built by a working data engineer, for analysts, data engineers, data scientists and software engineers who want a quiet, fast place to actually practice.