SQL Query CSV
Query CSV, JSON and Parquet files with real SQL in your browser. Powered by DuckDB WebAssembly: joins, GROUP BY, window functions. 100% local - files never uploaded.
How do I query a CSV file with SQL?
Click Load SQL engine, then add your file. It is automatically imported as a table named after the file, and you can immediately run queries like SELECT * FROM your_table.
Are my data files uploaded anywhere?
No. The whole DuckDB database engine runs as WebAssembly inside your browser tab. Files are registered into an in-memory local database and never leave your computer.
Which file formats are supported?
CSV and other delimited text (auto-detected separators), JSON and newline-delimited JSON, plus Parquet files — DuckDB reads them all natively.
Which SQL features are available?
Essentially full DuckDB SQL: SELECT with WHERE, GROUP BY, HAVING, ORDER BY, joins across multiple uploaded tables, CTEs, window functions, string/date functions and more.
How large can my files be?
DuckDB is highly optimized, so files of hundreds of megabytes usually work. Practical limits come from browser memory — a few GB of input is where most tabs give up.
Can I join two CSV files?
Yes. Add both files so each becomes a table, then write a normal SQL join, for example SELECT ... FROM a JOIN b ON a.id = b.id.
Can I rename or remove tables?
Yes. Each table chip has an editable name field — press Enter to rename (an ALTER TABLE runs underneath) — and a delete button that drops the table.
How do I export the query result?
After running a query, use the CSV or JSON export buttons above the result table to download the complete result set, not just the visible page.
Why does the first load take longer?
The DuckDB engine (about 33 MB) is downloaded once and cached by the browser. Later sessions start instantly and work offline.
What browsers are supported?
Any modern browser with WebAssembly support. Very old browsers without WebAssembly show a clear message instead of failing silently.
How to Use SQL Query CSV
This tool gives you a real SQL database in your browser. Drop in CSV, JSON or Parquet files, and DuckDB (compiled to WebAssembly) turns each one into a queryable table — joins, aggregations and window functions all run locally, with nothing ever uploaded.
- Press Load SQL engine once. DuckDB (about 33 MB) downloads and is cached by your browser for future sessions.
- Add CSV, JSON or Parquet files. Each becomes a table named after the file, listed as a chip with a rename field and a drop button.
- Type SQL into the editor and press Run query (or Ctrl+Enter). Use the Examples dropdown to get ready-made queries for the selected table.
- Browse paginated results (100 rows per page) and press the CSV or JSON export buttons to download the complete result set.
Register two files (for example orders.csv and customers.csv) and join them with normal SQL: SELECT ... FROM orders JOIN customers ON orders.customer_id = customers.id.
Related Tools
- SQLite Online Run SQLite queries in your browser. Open .db/.sqlite/.sqlite3 files or create an in-memory database, run multi-statement SQL, export results as CSV or JSON.
- CSV to JSON Converter Convert CSV to JSON online free. Supports custom delimiters, header-based objects, auto type detection. All processing in browser.
- CSV to XLSX Converter Free online CSV to XLSX converter. Convert CSV files to Excel workbooks in your browser. Multiple sheets, auto delimiter detection, UTF-8/GBK support. No upload, 100% private.
- Parquet Viewer Open Parquet files online and browse the data with pagination. Inspect the schema, view rows page by page and export to CSV or JSON - processed entirely in your browser.
- File Hash Checker Calculate and verify MD5, SHA-1, SHA-256, SHA-512 file hashes locally
- Chmod Calculator Free online chmod calculator to visualize and calculate Linux file permissions with checkboxes. Instantly convert between numeric (755, 644) and symbolic notation (rwxr-xr-x). Supports special permissions like setuid, setgid, sticky bit.
- ASCII Table Complete ASCII character encoding reference with decimal, hexadecimal, octal, binary codes, HTML entities, and character descriptions. Search and filter instantly.
- Hex Viewer View file contents in hex dump format with search, offset navigation, and virtual scrolling