Online SQL Playground
Write and run real SQL queries against sample databases directly in your browser. Powered by DuckDB compiled to WebAssembly, no signup, no installation, and nothing leaves your machine.
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Sample databases you can query
Pick a dataset from the selector above and its tables load instantly. Each one is small enough to reason about but rich enough to practise joins, aggregation, and window functions.
| Dataset | Tables | What it's good for |
|---|---|---|
| employees | departments, employees | Joins between two related tables, plus salary aggregation. |
| store | customers, products, orders | Multi-table joins and revenue aggregation across a retail schema. |
| school | students, courses, grades | GROUP BY and HAVING over a classic students-courses-grades model. |
| movies | movies, actors, ratings | Window functions and ranking over ratings and release years. |
| library | publishers, authors, books | Nested joins and subqueries across books, authors, and publishers. |
What you can do here
- Run any SELECT query: joins, GROUP BY, CTEs, window functions, and subqueries all work.
- Inspect the schema: table and column names are listed beside the editor so you never have to guess.
- Query your own CSV: upload a file and it becomes a table called
uploaded, queryable immediately. - Export results: download any result set as CSV.
- Modify data safely: INSERT. UPDATE, and DELETE affect only your browser session, and Reset DB restores the original data.
Frequently asked questions
- Is this SQL playground free?
- Yes. It is completely free with no account required. Your queries execute in your own browser, so nothing you write is uploaded or stored on a server.
- Which SQL dialect does the playground use?
- The playground runs DuckDB compiled to WebAssembly. Its syntax closely follows PostgreSQL, so standard ANSI SQL, window functions, CTEs, and most PostgreSQL functions work as expected.
- Can I query my own CSV file?
- Yes. Use the Upload CSV button and your file is registered as a table named 'uploaded' that you can query immediately, for example SELECT * FROM uploaded. The file never leaves your browser.
- Can I export my query results?
- Yes. Run a query and use the Download CSV button to save the result set as a CSV file.
- Do I need to install anything to run SQL here?
- No. There is nothing to install and no database to configure. The entire engine loads in your browser the first time you open the page.
- What happens if I modify or delete data?
- Changes only affect the copy of the database in your browser session. Use the Reset DB button to restore the selected dataset to its original state at any time.
Want structured problems instead of a blank editor?
Work through SQL practice problems with hints and solutions, follow the SQL lessons from beginner to advanced, or browse runnable query examples.