SQL Data Cleaning Studio

SQL Data Cleaning Practice

Practice real-world SQL cleaning on messy customer, HR, and healthcare datasets. Explore duplicates, NULLs, broken formats, invalid dates, outliers, and business-rule issues with guided missions and live query results.

NULLs, whitespace & text cleanup Duplicates & normalization Dates, outliers & rules Ctrl+Enter to run SQL
SQL Cleaning Playground
Inspect first with SELECT, then clean with TRIM, CASE, COALESCE, pattern checks, and dedupe logic.
Cleaning Output
Execution Status Ready

Load a dataset and run a query to inspect cleaned output.

Cleaning Coverage 0 focus areas

Mission focus appears here after dataset load.

Result Shape 0 rows

Rows and columns update after each query run.

Run a query to see cleaned output here.
Mission Brief
Mission loading Core

Dataset Clues
Cleaning Cheatsheet
Whitespace TRIM(), REPLACE()
NULLs NULLIF(), COALESCE()
Labels CASE WHEN ... END
Duplicates GROUP BY, HAVING
Ranking ROW_NUMBER()
Validation LIKE, GLOB, CAST()