SQL on CSV · lesson 6 of 10 · runs in your browser
The first aggregate: COUNT.
Aggregates collapse many rows into one answer. COUNT is the simplest: how many rows are there — or how many match a filter?
Aggregates collapse many rows into one answer. COUNT is the simplest: how many rows are there — or how many match a filter?
Every lesson runs a real SQL engine on real data, locally — no setup, no account, nothing uploaded. Your progress saves in your browser.
Each lesson is one concept with runnable examples — click any “try it” to load it into the editor.
Edit and run anything (Ctrl+Enter). The data is a real generated CSV — the same one every learner sees.
Exercises are verified by comparing your result against a reference — any correct query passes, not just one exact answer.
Ten lessons from SELECT to multi-column GROUP BY.
Your first SQL on a real CSV: SELECT * to see everything, LIMIT to take just a few rows.
Select only the columns you need and rename them with AS.
Filter CSV rows with WHERE: equality, greater/less than, text and numbers.
Combine filters with AND/OR and match text patterns with LIKE and % wildcards.