Stop spending hours on one task

AI assistant explains errors and suggests solutions — you learn faster

1SELECT class, COUNT(*)
2FROM students
3WHERE COUNT(*) > 5
4GROUP BY class
AI Assistant

It seems you are trying to filter the result after grouping.
The WHERE operator works before grouping. Use HAVING to filter grouped data.

Prepare for real interviews

Solve tasks that top companies actually ask in interviews

Alfa-Bank
MTC
Spotify
VK
Microsoft
Otkritie
Uchi
Samokat
Sber

Prove your skills to employers

Get a certificate after solving 50+ tasks successfully

Certificate Preview

Access to reference solutions

Solved but not sure it's optimal? We'll show you the best approach

Premium Account

Expand your free account features with full access to the site.

Login required before purchase
  • Unlimited hints from AI Assistant
  • Certificate of successful completion of SQL tasks in the trainer
  • Access to tasks from top company interviews
  • Access to reference solutions for tasks

Payment method

visamastercardmirsberpay
Russian bank card
visamastercardamericanexpressunionpay
Bank card
$ 36,90
6-month access

Our Users Love Us

Review avatar
Anna
After completing the course, I got promoted to data analyst. The course paid for itself in just one working day with my new salary!
Review avatar
Nikolay
Excellent presentation of the material! Very pleased with tasks from interviews at large IT companies.
Review avatar
Liza
The site is great! Tasks are interesting, UX is at a high level! Verification based on query results, not the query itself like on other sites.

FAQ

What tasks will open solutions
Premium expiration date
How to get a certificate
Will progress be saved if I purchase a premium subscription
What does the certificate look like
Will the certificate be available after the premium expires
Didn't find an answer to your question