SQL Query Logic vs Quarry

SQL Query Logic is an independent study app for learners who want to understand how SQL queries work, not just memorize syntax. It is built for beginners, students, analysts, developers, and interview candidates who need structured practice across fundamentals, practical skills, common pitfalls, and advanced concepts. Practice through 160 focused questions, each with a clear explanation so you can learn from every answer. - FSRS spaced-repetition intervals to review at the right time - Weak-point heatmap to show topics that need attention - Daily challenge for steady practice - Mock exams for timed review - Offline practice for commutes, travel, or quiet study - No login required Use it to review SELECT logic, joins, grouping, filtering, NULL behavior, subqueries, set operations, and reasoning patterns that often cause mistakes. Independent study app for SQL Query Logic practice. Not affiliated with, endorsed by, or sponsored by any company, certification body, exam operator, or vendor. All trademarks belong to their respective owners. Practice offline, no login required.

Quarry is a focused, offline gym for data and coding interviews. 108 hand-picked problems across SQL, pandas, and Python — write real code, run it on your device, and get graded instantly. Everything runs on-device. The SQL and Python engines are built into the app, so there's no sign-up, no internet requirement, and nothing you write ever leaves your phone or iPad. Practice on a plane, on the subway, or anywhere. WHAT'S INSIDE • 108 problems across three tracks: SQL queries, pandas data wrangling, and Python algorithms & data structures. • Real execution, real grading. Your output is checked against the expected result — no self-marking. • Company tags. Filter problems by 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. • Universal app — designed for both iPhone and iPad. PRIVATE BY DESIGN No accounts. No analytics. No ads. No tracking. Quarry collects nothing and works fully offline. Whether you're prepping for a data analyst, data engineer, data scientist, or software role, Quarry gives you a quiet, fast place to actually practice.