From your first SELECT to database architecture — four interactive courses with auto-checking in the browser. A free foundation (JOIN, aggregates, subqueries), then pick a direction: query optimization in PostgreSQL, SQL for analytics, or database design.
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The free basic course lays the foundation: SELECT, JOIN, aggregates, subqueries. Without it, any advanced course or interview will be harder than it needs to be.
Interactive course from scratch. You write queries right in the browser; the answer is checked automatically against a real database. SELECT, JOIN, aggregates, subqueries — everything you need to pass the SQL section of an interview.
Walk into an SQL interview confident — JOIN, GROUP BY, subqueries on autopilot
Close your own SQL tickets without escalating to the analytics team
Read SQL in teammates' pull requests — no more 'um, not sure'
After the basic course you write SQL confidently. Where you go next is up to you: some focus on performance, some on analytics, some on data architecture. We have an advanced course for each direction — deep, on real-world problems.
Stop guessing why your queries are slow. Learn to read EXPLAIN, pick indexes for specific tasks, and speed up queries by 100x+ on real production cases.
Close 'this query is slow' tickets yourself — via EXPLAIN, indexes, statistics
Cut latency on slow production queries by 10–100×
Explain to your team why the planner picked this plan
Learn to answer product questions right in the database — no dumping into Python or BI tools. You'll master pivot tables, time series analysis, retention, funnels, and user segmentation — all in pure SQL.
Answer product questions in Slack in minutes, not days
Build cohorts, funnels, and retention in pure SQL — no Python exports
Stop hitting the GROUP BY ceiling — windows and time series handle 80% of cases
From the first table to a live system under load. Learn not to memorize answers but to spot the forks: which key, which type, which lock, how to migrate the schema without taking prod down.
Design schemas that won't be rewritten in a year under load
A small set of patterns covers most SQL interview tasks. You learn to recognize them by their signal words and pull out a ready-made skeleton — on real tasks from Ozon, VK and Yandex.
You read the statement and see the construct at once, even on an unfamiliar task
You solve in minutes what looks unsolvable without practice
You walk into the interview confident — every pattern already solved ten ways
