DB Learn

DBLearn is a complete, offline-first course on databases and SQL — designed to take you from "what is a database?" to enterprise-level schema design, no internet connection required. WHY DBLEARN? Most SQL apps are either flashcard quizzes or bare-bones playgrounds. DBLearn combines both with a structured curriculum, so every concept you learn is immediately backed by hands-on practice on real SQLite databases — right on your device. WHAT YOU'LL LEARN DBLearn takes you through 6 in-depth chapters, from foundational concepts to production-ready database design: - What is a database? — data vs information, flat file problems, database types, DBMS architecture, SQLite internals, and ACID properties - Tables & relations — table anatomy, data types, primary keys, foreign keys, constraints, and normalisation (1NF through 3NF) - SQL basics — SELECT statements, filtering with WHERE, aggregate functions and GROUP BY, INSERT/UPDATE/DELETE, sorting, pagination, and string/date functions - JOINs — INNER JOIN, LEFT JOIN and anti-joins, multi-table joins, self joins, and subqueries (scalar, IN, EXISTS, derived tables) - Advanced SQL — CTEs and recursive queries, window functions (RANK, LAG, LEAD), transactions and savepoints, query optimisation with EXPLAIN, views and triggers - Enterprise design — ER diagrams, schema migrations, common design patterns (soft deletes, audit logs, state machines), and performance tuning at scale EVERY LESSON IS STRUCTURED FOR LEARNING Lessons combine clear explanations, annotated code examples, key-term callouts, "try it yourself" prompts, and diagrams — so concepts stick before you move on. SQL PLAYGROUND — WRITE REAL QUERIES Practice on multiple pre-loaded sample databases (e-commerce, school, hospital, and HR), each with realistic schemas and seed data. Write and run any SQL — SELECT, JOIN, CREATE TABLE, and more — and see results instantly in a clean, terminal-inspired interface. You can also create your own custom databases from scratch and design your own schemas. Features include: - Query history with timing and error tracking - Saved query snippets with tags - Table browser with schema, foreign keys, and row counts - CSV export of results - Reset any database back to its original seed data CHAPTER QUIZZES — 500+ QUESTIONS Test your understanding with quizzes drawn from a pool of 500+ questions across all difficulty levels — easy, medium, hard, and expert. Each session gives you 50 random questions with detailed explanations after every answer, plus a review of anything you got wrong. SQL CHALLENGES — SOLVE REAL PROBLEMS Put your skills to the test with 24 hands-on coding challenges, from simple SELECT statements to expert-level window functions, cohort analysis, and running totals. Each challenge includes hints, sample solutions, and instant validation against expected results. TRACK YOUR PROGRESS DBLearn keeps track of completed lessons, quiz scores, and solved challenges — all stored locally on your device. See your overall progress at a glance from the home screen, with per-chapter completion tracking. 100% OFFLINE — NO ACCOUNT NEEDED There are no logins, no ads, and no internet connection required. Everything — lessons, the SQL playground, quizzes, and your progress — works completely offline using a local SQLite database. WHO IS THIS FOR? - Students learning databases for the first time - Developers brushing up on SQL fundamentals - Anyone preparing for technical interviews involving SQL - Self-learners who want a structured path from beginner to advanced Whether you're writing your first SELECT statement or optimising complex queries with window functions, DBLearn gives you the theory, the practice environment, and the feedback to actually learn database mastery — at your own pace, anywhere.