Write SQL in the editor above, press Run, and read the results below it. The engine is a real SQLite database compiled to WebAssembly, running on your machine — not a mock parser and not a server that receives your queries. Scripts execute statement by statement, so a script that creates a table, inserts rows, and selects them back shows you every step, and the database stays alive between runs.
How the SQL compiler works
The editor accepts a whole script, not just one statement. Every statement runs in order inside the worker: CREATE TABLE builds the schema, INSERT fills it, and SELECT returns a result table you can scroll, inspect, and copy as CSV. Statements that change data report how many rows they touched, so UPDATE and DELETE feel like the real thing — because they are. When a statement fails, execution stops there, the error message from SQLite appears with the exact statement that caused it, and everything before it keeps its effect, exactly like the sqlite3 shell.
The database persists across runs for as long as the page is open. That means you can build a schema in one run, query it in the next, and iterate on a JOIN until it’s right — the workflow you’d have with a local database, minus the installation. The Reset button (or switching the sample database) starts over from a clean database.
Sample databases and the schema browser
Three ready-made databases come with the tool: Employees (departments, salaries, hiring dates), Library (authors, books, loans), and Store (products, customers, orders). Each is small enough to understand in a minute and realistic enough to practice real queries — joins, aggregates, date handling. Prefer to start clean? Choose the empty database and build your own tables.
The Schema tab lists every table and view in the current database with its columns, types, primary keys, and row counts. The SELECT * button next to each table runs a quick inspection query without touching your editor. As your scripts create and drop tables, the schema view updates after every run — and the editor’s autocompletion learns your table and column names as you type.
What SQL can you practice here?
The engine is SQLite, the most widely deployed database in the world — the same one in your phone, your browser, and half the apps you use. You can practice the full core of the language: SELECT with WHERE, ORDER BY, and LIMIT; inner and outer JOINs; GROUP BY with HAVING; subqueries and common table expressions (WITH); window functions like OVER (PARTITION BY …); date and string functions; indexes and views; and transactions. If you are following the SQL curriculum on this site, every lesson example runs here unchanged.
The honest limits: engine-specific features of MySQL, PostgreSQL, or SQL Server — like AUTO_INCREMENT spelling, stored procedures, or RETURNING clauses outside SQLite’s support — behave the SQLite way or don’t exist. That’s the right trade-off for learning: SQLite’s dialect is close to the standard, and the concepts transfer directly.
Your queries stay on your device
Everything runs in your browser via WebAssembly. The query you write is saved only in your browser’s local storage, so closing the tab and coming back restores your last edit. The share button packs the current script into the link itself — the URL fragment is never sent to any server, and whoever opens it sees exactly what you wrote. Import opens a .sql file from your computer; Download saves the current script; Copy puts it on your clipboard. There is no account and nothing to clean up afterwards.
Frequently asked questions
Which SQL dialect is this? SQLite 3, shown in the status bar with its exact version. It covers the SQL core that every engine shares.
Do tables survive between runs? Yes — until you press Reset, switch the sample database, or reload the page. Each page load starts fresh.
Can I use it on a phone? Yes. The editor and results stack vertically on small screens, and the result tables scroll sideways within their cards.
Why is the first run slower? That is the one-time download of the SQLite engine (about 650 KB). Every run after it starts instantly.
Can I export results? Yes — every result table has a Copy CSV button, and result sets larger than 500 rows tell you when they were truncated.