SQL Practice

Twenty-six short, hands-on SQL lessons, from a single SELECT all the way past joins into subqueries, window functions, transactions, many-to-many joins, CTEs, CASE, UNION, ALTER TABLE, and self-joins. Each lesson gives you a task, a live database, and a Run button - you write the query, run it, and get checked instantly. Everything runs in your browser.

The last six are the ones that matter at work, where the query runs, returns a result, and is still wrong: a single NULL that empties a NOT IN, a join that quietly doubles your revenue, a status column everyone forgets, a typo that splits one company into three, and two capstones where the hard part is pinning down what the question actually means.

Start with lesson 1. You can leave and come back any time - your code is saved locally.