Be sure of the number before you say it.
For beginners · 10 days · ≈ 5 hoursPlace an order in a shop and watch it turn into a row, then build your first query by tapping. About ten minutes, no typing yet.
Place an order in the shop and watch it become a row in a table. Tap through columns, find empty values, build a query without typing.
As you write a query, you see how the database will read it: take the table, keep the rows, sort. Errors are explained in plain words.
Every query also runs on a second dataset with different numbers. You can't guess the answer — but the check recognises and explains the usual mistakes.
Place a practice order and find it as rows in a table. Then build your first query by tapping: no typing yet.
Optional independent practice after the lesson.
SELECT and FROM by hand: type queries, calculate inside them and fix someone else's.
Optional independent practice after the lesson.
WHERE, AND and OR, sorting and a “top 5”. Plus the sneaky empty value that isn't even equal to itself.
Optional independent practice after the lesson.
IN, BETWEEN, LIKE and dates — shorter, sharper conditions. And CASE labels rows: “cheap”, “medium”, “expensive”.
Optional independent practice after the lesson.
Nine thousand orders — in one number. COUNT, SUM, AVG, your first real metric and GROUP BY.
Optional independent practice after the lesson.
Orders and people are different numbers. We slice GMV by week and by order size, and count the cancellation rate in one row.
Optional independent practice after the lesson.
Some questions can't be answered in one query. A subquery and WITH break them into steps that read from top to bottom.
Optional independent practice after the lesson.
JOIN connects tables by a shared code, and LEFT JOIN finds what has no match: products nobody has ordered.
Optional independent practice after the lesson.
SQL's sneakiest trap: a join quietly multiplies rows and the total balloons. We learn to spot it and get around it. And we join on a range of dates.
Optional independent practice after the lesson.
Window functions calculate a share, a place in a group and a running total without collapsing rows. At the end — a report for the board that brings together two weeks of work.
Optional independent practice after the lesson.
The dashboard shows a record week after a promotion. You find out what really happened to the money.
Days 1–2 without an account; all 10 days with a free account
SQL is free: all 10 days of Start with a free account. You pay only for practice: case rounds (€19) and Meridian (€59).
€19Atterna Foundations
one-time · early-access price