The latest articles on DEV Community by Martin (@martinl5). https://dev.to/martinl5 https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3970629%2F57d46621-101d-4087-894a-c8e80d7218fe.jpeg https://dev.to/martinl5 en Martin Sat, 06 Jun 2026 03:02:22 +0000 https://dev.to/martinl5/i-built-a-free-sql-practice-game-where-you-work-at-a-fictional-singapore-bank-4728 https://dev.to/martinl5/i-built-a-free-sql-practice-game-where-you-work-at-a-fictional-singapore-bank-4728 <p>I've been frustrated with SQL learning resources for a while. Most are either:</p> <ul> <li>Dry reference docs</li> <li>Toy exercises with no context ("SELECT * FROM employees")</li> <li>Paid platforms with paywalls after level 3</li> </ul> <p>So I built <strong><a href="https://sqlwak.vercel.app" rel="noopener noreferrer">SQLwak</a></strong> — a free, browser-based SQL game where you're hired as a Graduate Analyst at <strong>Lion City Bank</strong>, a fictional Singapore bank.</p> <h2> How it works </h2> <p>Instead of abstract exercises, every challenge is a real business request from a colleague:</p> <blockquote> <p><em>"The Operations team needs all Central region branches for an upcoming audit."</em></p> <p><em>"Risk wants customers with credit scores below 600 who have active loans."</em></p> <p><em>"Finance needs vessels ranked by cargo revenue — use window functions."</em></p> </blockquote> <p>You write actual SQL against a realistic 9-table banking database and get immediate feedback.</p> <h2> 57 levels across 4 tiers </h2> <div class="table-wrapper-paragraph"><table> <thead> <tr> <th>Tier</th> <th>Skills</th> </tr> </thead> <tbody> <tr> <td>🟢 Foundational</td> <td>SELECT, WHERE, ORDER BY, LIMIT</td> </tr> <tr> <td>🟡 Intermediate</td> <td>JOINs, GROUP BY, HAVING, subqueries</td> </tr> <tr> <td>🔴 Advanced</td> <td>CTEs, multi-table aggregations</td> </tr> <tr> <td>⚫ Expert</td> <td>Window functions (RANK/DENSE_RANK OVER PARTITION BY), UNION ALL, compound CTEs</td> </tr> </tbody> </table></div> <h2> The database schema </h2> <p>Lion City Bank has two divisions:</p> <p><strong>Retail Banking:</strong> customers, accounts, transactions, loans, branches, products</p> <p><strong>Maritime Trade Finance</strong> (Advanced/Expert levels): vessels, cargo_shipments, trade_finance_facilities — covering voyages between Singapore, Port Klang, Bangkok, Jakarta, and Ho Chi Minh City.</p> <p>The maritime division exists because Singapore is a major trade hub. It makes the Expert levels genuinely interesting — you're ranking vessels by cargo revenue and analyzing trade finance utilisation rates, not just counting rows.</p> <h2> Technical details </h2> <ul> <li> <strong>Next.js 15</strong> + TypeScript + Tailwind CSS</li> <li> <strong>SQLite via WebAssembly</strong> — all query execution is client-side, no backend needed</li> <li>Deployed on <strong>Vercel</strong> </li> <li>Fully open source: <a href="https://github.com/martinl5/sqlwak" rel="noopener noreferrer">github.com/martinl5/sqlwak</a> </li> </ul> <h2> No signup. No download. Just SQL. </h2> <p>Open the link and start writing queries: <strong><a href="https://sqlwak.vercel.app" rel="noopener noreferrer">sqlwak.vercel.app</a></strong></p> <p>Would love feedback on difficulty progression, new level ideas, or schema additions. What SQL concepts do you wish you'd practiced more before your first data job?</p> sql database beginners webdev