Learn SQL - Database & Queries

Learn SQL by writing queries against a real database on your phone. Short lessons explain each idea, then you type the statement, run it and see the rows come back. It is an SQL tutorial, a database course and an SQL practice lab in one app, with an AI mentor for the join that will not behave.

WHAT'S INSIDE
• 46 courses with 183 lessons, from SQL for beginners (A1) to advanced database topics (C2)
• A database on your device: SQLite runs your code on the phone, and lessons that need PostgreSQL syntax run in PostgreSQL on the phone too. No server round trip, and your tables stay between sessions
• SQL editor and sandbox: write anything, browse the schema, reopen earlier statements from the history and see the plan with EXPLAIN
• Practice tables ready to use: users, orders, order items, products, categories, employees, departments, sales and events
• Daily Query: one SQL query to write each day, checked against the data on your phone
• 20 guided database projects, checked by the result you get, not by the text you typed
• 30 missions (easy, medium, hard)
• World Coding Challenge: 3 global rounds every day
• Quizzes, flashcard review, a cheat sheet, interview questions, streaks and a skill tree
• Final exam and certificate (Pro)

THE ARENA: PRACTICE GAMES
• Data Detective: 6 cases, where each correct answer unlocks the next clue
• Dataset packs: films, football matches, albums and weather, with guided questions
• Your own data: import a CSV or JSON file and explore it (CSV export with Pro)
• Duel: three tasks against a target pace
• Golf: return the same rows with a cheaper plan
• Fix It: a statement that runs but returns the wrong rows, with a row-by-row diff
• Drills: spaced review built from your own mistakes
• Schema Designer: design tables, get lint hints and run the generated DDL
• Interview Simulator: 5 timed questions and a follow-up, then a report
• Rush: a 60-second game with a combo score

WHAT YOU'LL LEARN
• SELECT, WHERE, ORDER BY, LIMIT and filtering patterns
• Aggregate functions, GROUP BY and HAVING
• JOINs: inner, left, self joins and advanced patterns
• INSERT, UPDATE, DELETE, NULL handling, CASE, dates, strings and numbers
• Constraints, keys and database design
• Subqueries, CTEs, recursive queries and window functions
• Views, JSON and JSONB, arrays, GROUPING SETS, ROLLUP and CUBE
• Performance: EXPLAIN, indexes, transactions and concurrency
• Triggers, stored procedures, row-level security, backup and restore
• Partitioning, replication, data warehousing and sharding
Most lessons teach standard SQL. The advanced courses use PostgreSQL features.

HOW A SESSION LOOKS
1. Answer today's question or continue your lesson
2. Read a short explanation and try the example, many with a Run button
3. Open the editor, change the code, run it and read the result table
4. Ask the AI mentor why a join returns too many rows

WHO IT'S FOR
• Beginners starting from zero
• Analysts and marketers who want to pull their own data
• Developers adding databases and PostgreSQL to their skills
• Students and career-switchers heading into data roles
• Anyone doing SQL interview prep

FREE AND PRO
Free: the first course (Introduction to SQL & Databases), a preview of every other lesson, the editor and sandbox, the Daily Query, 1 guided project, 2 missions, part of every Arena mode (for example 3 duels and 3 drills a day, 1 case and 1 dataset pack) and a daily AI mentor allowance. The free version shows ads.
Pro: every course and lesson, all projects and missions, the full Arena, the final exam and certificate, AI tools, AI mentor without the daily limit, and no ads. Pro is a weekly, monthly or yearly subscription, or a one-time lifetime purchase.

The app is available in 22 languages.

Learn SQL is an independent app, not affiliated with the PostgreSQL Global Development Group or the SQLite project.