📚 Resources 12 — Go Deeper on Databases & SQL

All free. All browser-based. Pick one interactive site and stick with it — they cover similar ground in different voices.

🖱️ Interactive SQL practice

SQLBolt — the lab’s pick: short lessons with a live database in the page, no sign-up. Best for absolute beginners who want gentle, bite-sized steps.
SQLZoo — a long-running classic with progressively harder exercises against fun datasets (world countries, Nobel prizes). Best for learners who finished SQLBolt and want more mileage.
Khan Academy — Intro to SQL — video walk-throughs paired with in-browser coding challenges, in Khan Academy’s famously patient style. Best for people who like being talked through each step.
W3Schools SQL Tutorial — the internet’s reference desk for SQL: every keyword on its own page with a “Try it yourself” button. Best kept open as a lookup while you practice elsewhere.

Crash Course Computer Science — the series’ episodes on data structures and files (episodes 14 and 20) show what’s underneath a database’s shelves. Best for connecting this module back to Modules 01 and 11 in animated form.

Wikipedia — “Database” — heavier reading than this course, but a solid, stable overview with history included. Best for the curious reader who wants to know how we got from punch cards to MongoDB.