Learn SQL from zero on a realistic marketplace dataset: a 10-day plan

SELECT COUNT(DISTINCT buyer)
FROM orders
WHERE status = 'paid';

Most SQL tutorials teach syntax on toy tables. That is fine for learning what WHERE does, but you also need practice deciding what to do when a colleague asks “which categories bring in the most money?” and the data has cancelled orders, refunds and items on separate rows.

This plan follows Atterna Start, our course from zero. You join the analytics team of a fictional marketplace, Meridian, as an intern; every day colleagues bring real questions, and every query is checked automatically on two different extracts of the data — which helps catch queries that fit one extract accidentally. Passing these checks is useful feedback, not proof of correctness on every possible dataset.

Short version: ten sessions you can work through at your own pace. Week one: tables, first queries, filters, counting and breakdowns. Week two: queries in steps, joins, join traps and window functions. Days 1–2 run in your browser with no account and nothing to install; a free account opens all ten.

Week one: reading data and counting

Week two: steps, joins and windows

After day 10 comes the first episode of the Meridian simulator, where the same skills meet an unclear request and a decision.

What makes it stick

• Hands first, syntax second. You click through a table and build a query with the mouse before typing one.
• SQL you can read aloud. As you type, you see how the database reads the query: take the table, pick the rows, group, sort.
• Honest checks. Your answer runs on two extracts with different data; the usual mistakes are recognised and explained in plain words.
• Real questions. “Which home products under €30 do we have in stock?” rather than “select all cats older than 3”.

FAQ

Can I learn SQL in 10 days?

The ten sessions introduce filters, grouping, joins, CTEs and a first window function. How quickly they become comfortable depends on your starting point and practice. Finishing the course is not a guarantee of fluency or job readiness.

Is the course free?

Days 1 and 2 are free and need no account. A free account opens all ten days, case 1 and Meridian episode 1, and keeps your progress on any device. You pay only for practice beyond that: case rounds in Atterna Foundations (€19) and the Meridian simulator in Atterna Analyst (€59), both one-time early-access prices, not a subscription. To buy, leave a request on the access page; Kirill replies within 24 hours with how to pay.

Do I need to install anything?

No. SQL runs in your browser on a copy of the marketplace data; checks happen automatically.

Which SQL dialect does it use?

Queries run on DuckDB in your browser. The core ideas — SELECT, JOIN, GROUP BY, WITH, window functions — transfer to PostgreSQL, BigQuery and Snowflake. Some functions, date expressions and other syntax differ by engine; check its documentation when porting a query.

I already know some SQL. Where should I start?

Take the six-question level check: it suggests a starting point — a day of the course, or the Meridian simulator if you already write SQL.