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SQL PracticeOnline — free exercises with instant feedback

Reading about SQL only gets you so far. DB Quacks lets you practice SQL online by writing real queries against real data, right in your browser. Every solution is checked instantly — no signup, no install.

Practice by doing, not by watching

SQL is a skill, and skills are built through repetition. On DB Quacks every exercise runs your query through DuckDB-WASM and compares the result to the expected answer, so you know immediately whether you got it right. When you are stuck, experiment freely in the editor — running a query and seeing what comes back costs nothing.

Ways to practice

• Guided exercises: the 38-level tutorial introduces one concept at a time with a matching exercise for each.
• Story-driven challenges: the challenges put your skills to work — help Duckbert scout the Great Duck Migration, or crack the case of the vanished presents in the Christmas Heist.
• Weekly challenge: one fresh SQL puzzle every week — solve it in as few guesses as you can and see how you rank.

What you can practice

Cover the full range of everyday SQL: selecting and filtering rows, sorting and limiting, joining multiple tables, grouping and aggregating, and stepping up to subqueries, CTEs, and window functions. Because the exercises are graded on the actual query result, you learn to think about what the data should look like — the mindset that matters in real analytics work.

Who this is for

Whether you are preparing for a data analyst interview, reinforcing a class, or brushing up rusty skills, structured practice with instant feedback is the fastest way to improve. Start easy and climb toward harder problems at your own pace.