98 levels · 9 tiers · 3 060 exercises

Master SQL
through practice

Real exercises, instant feedback, explained errors. From basic SELECT to window functions and CTEs — one level at a time.

SELECTWHEREJOINGROUP BYORDER BYHAVINGSubqueriesCTEsWindow Fns

How it works

The right way to learn SQL

Three pillars that make the difference between reading docs and actually mastering SQL.

📖

Learn

Every level opens with a focused lesson. Understand the concept before writing a single line of SQL.

  • Lesson card before each level
  • Syntax explained in plain words
  • Concrete real-world examples

Practice

Up to 50 exercises per level, each pushing your understanding a little further.

  • Progressive difficulty
  • Instant query execution
  • Side-by-side result comparison
🧠

Understand

When you make a mistake, you know exactly why. No cryptic error — a clear explanation of what went wrong.

  • Pedagogical error messages
  • Expected vs actual output
  • Specific column & table hints

Live demo

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query.sql — Level 45 · Window Functions

Learning path

A structured journey

9 tiers, 98 levels. From zero to SQL expert — step by step.

1
SELECT
2
WHERE
3
ORDER BY
4
GROUP BY
5
JOIN
6
Subqueries
7
Window Fns
8
CTEs
9
Advanced
Beginner
Expert

98

Levels

3060

Exercises

9

Tiers

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