PostgreSQL Exercises
Practice SQL against a real sample database in the browser. Free, no registration, and it checks your answer.
It goes from basic SELECT all the way to window functions and recursive CTEs, which is the part most people skip and then meet in an interview. Extremely helpful for interview prep, or for getting SQL back after a year of writing application code.
Big thanks to Alisdair Owens for creating and maintaining this fantastic resource!
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