What SQL dialect do these challenges use?

We use the SQLite dialect for our in-browser engine. It perfectly supports all standard SQL logic including inner joins, aggregations, common table expressions (CTEs), and modern window functions.

Can I save my progress?

Yes. Your solved challenges and active streaks are automatically saved to your browser's local storage. Furthermore, any query you type is auto-saved, meaning you can leave a complex problem halfway through and return to it perfectly intact tomorrow.

Are these challenges free?

Absolutely. All SQL challenges on Coders.sh are completely free to solve. Our goal is to provide a world-class practice environment for developers without any paywalls or registration barriers.

Do I need to install a database locally?

No. Our playground uses a WebAssembly-based SQLite engine that runs entirely in your browser. Every challenge comes with pre-seeded data, so you can start writing queries instantly.

How do I check if my answer is correct?

When you submit a query, we compare your result set against our secret "Golden Answer" data. We check for row count, column order, and exact data matches to ensure your logic is 100% correct.

SQL Challenges - Free Interactive SQL Practice Online

Challenge library

Browse realistic SQL problems by difficulty and topic, then solve them instantly in the browser. This library is built for hands-on practice, interview prep, and sharpening production-style query skills without local setup.

25 challenges

Title	Complexity	Status	Solve
The Ghost of 2020	Easy	Not solved	Solve
The Skimming Intern	Medium	Not solved	Solve
Git Blame Detective	Medium	Not solved	Solve
The Shadow Follower	Hard	Not solved	Solve
The Slow Query Hunt	Medium	Not solved	Solve
Deadlock Recovery	Easy	Not solved	Solve
The Equity Heist	Medium	Not solved	Solve
Zombie Accounts	Medium	Not solved	Solve
The Data Leaker	Hard	Not solved	Solve
The Recursive Tree	Hard	Not solved	Solve
The Vanishing Log	Medium	Not solved	Solve
The Referral Loop	Hard	Not solved	Solve
Inventory Leak	Hard	Not solved	Solve
The Botnet Filter	Hard	Not solved	Solve
The Partial Plate	Easy	Not solved	Solve
The Midnight Shifter	Medium	Not solved	Solve
The Loyalty Gap	Medium	Not solved	Solve
Slowest Endpoint	Medium	Not solved	Solve
The Accidental Duplicator	Medium	Not solved	Solve
The Ghost Feature	Medium	Not solved	Solve
The Org Chart Leak	Hard	Not solved	Solve
The Churn Predictor	Hard	Not solved	Solve
The Double-Spent Token	Medium	Not solved	Solve
The Session Stitcher	Medium	Not solved	Solve
The Nearest Neighbor	Easy	Not solved	Solve

What this challenge library helps you practice

These SQL challenges are built around the kinds of problems that show up in analytics work, backend systems, and interview prep: filtering noisy data, joining the right tables, validating business logic, and returning results that are actually correct.

Instead of isolated syntax drills, you work through realistic scenarios where query structure, edge cases, and result accuracy matter just as much as remembering the right clause.

Why this is worth practicing on

This library is built for hands-on SQL practice that feels closer to real query work than static drills or syntax-only question banks.

Realistic seeded datasetsReal query execution, not static quizzesExact result validationProgress and drafts saved in browserFocused challenge library without paywall friction

What makes the practice useful

Real-world scenarios

Challenges use production-like tables and business logic—not toy examples—so you practice choosing the right approach, not just syntax.

Learn by doing

Write queries in the browser, run them instantly, and fix mistakes with immediate feedback. That loop builds confidence faster than passive tutorials.

Interview-ready patterns

Practice joins, aggregations, filtering edge cases, and tricky “easy” questions that show up in data and analytics interviews.

Progressive difficulty

Start with fundamentals, then move to subqueries, joins, and advanced topics like window functions and CTEs as you improve.

How difficulty is structured

Challenges are tagged Easy, Medium, or Hard so you can practice at the right level. Easy focuses on SELECTs and filters; Medium adds joins and aggregations; Hard covers subqueries, window functions, and multi-step logic.

Use the filters above the table to focus on one level, or work through the catalog in the order that matches your current goal.

FAQs

What SQL dialect do these challenges use?
We use SQLite in the browser. It supports standard SQL including joins, aggregations, CTEs, and window functions.
Can I save my progress?
Yes. Solved challenges and your in-progress queries are saved in your browser’s local storage—no account required.
Are these challenges free?
Yes. Every SQL challenge on coders.sh is free to solve, with no paywall or registration.
Do I need to install a database locally?
No. A WebAssembly SQLite engine runs in your browser. Each challenge ships with pre-seeded data.
How do I check if my answer is correct?
Submit your query and we compare your result set to the expected output—row count, columns, and values must match.

Ready to test your SQL?

Pick a challenge from the table above and start writing queries.

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