PracticeData

Master data skills, one exercise at a time.

SQL today. Pandas tomorrow. Zero setup — runs entirely in your browser.

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What is PracticeData?

PracticeData is an open-source, browser-based platform for practicing real-world data skills. No database to install, no environment to configure — just open the app and start writing queries.

Powered by DuckDB-WASM, everything runs locally in your browser. Your progress is saved automatically.

Features

• 101 exercises across beginner, intermediate, and advanced modules
• 8 company scenarios — NeonCart, DataFlow, PixelAds, CashBee, TalentHub, CloudForge, FreshBowl, StreamPulse — each with its own data and business questions
• 2 career tracks — Data Analyst (50 exercises) and Data Engineer (51 exercises), with shared foundations and specialized paths
• Real business scenarios — every exercise is framed as a question a data team would actually ask
• Instant feedback — submit your query, see results and validation in real time
• Bilingual — full EN/FR support with one-click toggle
• Dark & light mode — easy on the eyes, day or night
• Activity tracking — GitHub-style contribution graph to keep you motivated
• Progress by module — track completion across structured learning paths
• 100% client-side — no backend, no account, no data leaves your browser

Career Tracks

Data Analyst

From SELECT basics to FAANG-level analytical SQL.

Level	Modules	Exercises	Topics
Beginner	B1-B4	26	SELECT, aggregation, basic joins, NULL handling
Intermediate	I1-I7	16	Multi-table joins, CTEs, subqueries, window functions, anti-joins
Advanced	A1-A8	8	Running totals, gaps & islands, cohort retention, funnel analysis

Data Engineer

From schema design to pipeline SQL, optimization, and data quality.

Level	Modules	Exercises	Topics
Beginner	B1-B4	26 (shared)	SELECT, aggregation, basic joins, NULL handling
Intermediate	DE-I1-I2	10	DDL, DML, data types, constraints
Advanced	DE-A1-A8	41	Star schema, SCD Type 2, MERGE, incremental loads, data quality

Company Scenarios

Practice on realistic company datasets with multi-exercise storylines.

Company	Sector	Difficulty
NeonCart	E-commerce	Beginner
FreshBowl	Foodtech / Delivery	Beginner
PixelAds	Marketing / Adtech	Intermediate
TalentHub	HR / Recruitment	Intermediate
CloudForge	Data Platform	Intermediate-Advanced
DataFlow	SaaS B2B	Intermediate-Advanced
CashBee	Fintech	Advanced
StreamPulse	Streaming / Media	Advanced

Tech Stack

Layer	Technology
Framework	Next.js 16 (App Router)
Language	TypeScript (strict mode)
SQL Engine	DuckDB-WASM
Editor	CodeMirror 6
UI	shadcn/ui + Tailwind CSS
Tables	TanStack Table + React Virtual
State	Zustand (localStorage persistence)
Testing	Vitest (unit + integration against native DuckDB)

Quick Start

git clone https://github.com/lucaszub/sql-practice.git
cd sql-practice
pnpm install
pnpm dev

Open http://localhost:3000 and start practicing.

Scripts

Command	Description
pnpm dev	Development server
pnpm build	Production build
pnpm test	Run unit tests (watch mode)
pnpm test:run	Run unit tests (single run)
pnpm test:integration	Validate all exercises against native DuckDB
pnpm lint	ESLint

Project Structure

src/
  app/                          # Next.js pages
    (main)/
      page.tsx                  # Home — exercise list with filters
      roadmap/
        data-analyst/           # DA track roadmap
        data-engineer/          # DE track roadmap
      companies/                # Company selection page
      company/[companyId]/      # Company scenario workspace
    exercise/[id]/              # Exercise editor + validator
  components/                   # React components (shadcn/ui)
  exercises/                    # 101 exercises
    {id}/
      exercise.ts               # Schema, solution, test cases, explanation
      exercise.test.ts          # Unit tests
  lib/
    companies/                  # Company profiles (schema, exercises, metadata)
    db/                         # DuckDB init, query runner, validator
    exercises/                  # Types, registry, module/track definitions
    i18n/                       # EN/FR translations
    store/                      # Zustand stores (progress, session)

Adding Exercises

Each exercise lives in src/exercises/{id}/ with two files:

• exercise.ts — schema SQL, solution query, test cases, explanation
• exercise.test.ts — unit tests (structure + mock validation)

Conventions:

• Business-framed descriptions ("The marketing team wants to...")
• 10-30 rows per table, deterministic data, include NULLs
• Minimum 2 test cases (default + edge case)
• DuckDB-compatible SQL only
• Register in src/lib/exercises/index.ts and assign to a module in modules.ts

Roadmap

• Beginner SQL — 26 exercises (B1-B4: SELECT, aggregation, joins, NULL handling)
• Intermediate DA — 16 exercises (I1-I7: multi-table joins, CTEs, window functions, anti-joins)
• Advanced DA — 8 exercises (A1-A8: cohort retention, funnel analysis, revenue metrics)
• Intermediate DE — 10 exercises (DE-I1-I2: DDL, DML, data types)
• Advanced DE — 41 exercises (DE-A1-A8: star schema, SCD2, MERGE, incremental loads, data quality)
• Two career tracks with dedicated roadmap pages
• 8 company scenario profiles with interactive SQL workspace
• Bilingual EN/FR interface
• Global footer with GitHub link
• Company CTA banners in roadmap level sections
• Pandas exercises

Contributing

Contributions are welcome! Whether it's a new exercise, a bug fix, or a UI improvement — open an issue or submit a PR.

License

MIT