SQL from scratch
From your first SELECT to window functions and transactions: theory, a walkthrough and a task after every lesson — in the browser, with no database to install.
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Vault-9 · station levels
The whole station on one map
The year is 2184; the archive station Vault-9; QUERY, the AI mentor. Every course is a level of the station and a part of one story: the signal that was caught, the far archive that was opened, the engine room that was restarted. This page shows where you are and where to go next.
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chapters across the courses
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lessons
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lessons for free
Counted across the open courses — everything you can start today.
Where you board the station
Level 1→ start here
The foundation · The first signal
The language the whole station speaks. Every other level opens from here — and this is the only place where the order really matters.
Level 2
The branches
From here the levels fan out. There is no queue between them: take the one you came for, the others are not going anywhere.
Level 3
The intake level · Where the data arrives
Where data reaches the station before anyone else sees it. Needs both SQL and Python.
How to read this map
A level is not a queue
Inside a level the courses are peers and carry no numbers. There is exactly one order: SQL is the language all the others speak.
Progress is counted per course
Every card shows its own progress. A finished course does not fill in its neighbour: the courses are not lined up, so a single overall percentage would be a lie.
Every course has free chapters
The opening chapters of each course are open without a subscription: start today and decide about Pro later.
One story, several ways in
QUERY is waiting on every level. Start with what you came for: the station does not ask to be walked through in order.