# Let's Data Science

> Interactive data science learning platform with 1,625 SQL and Python coding
> problems across 15 industry datasets, 13 active interactive courses with animated
> visualizations, 496 interview flashcards, and AI-curated news. All code
> execution runs in-browser via sql.js (SQLite WASM) and Pyodide (Python WASM).
> No installation required.

The platform covers the full data science learning journey: structured courses
(SQL, Python, Statistics, Probability), hands-on practice with real company-style
datasets (AdTech, Banking, Fintech, Healthcare, Logistics, Retail, and 9 more),
rapid interview prep via flashcards, and daily AI/ML news with relevance scoring.

## Practice Problems
- [All Problems](https://letsdatascience.com/problems): 1,625 SQL and Python practice problems graded in-browser (816 SQL, 809 Python)
- [AdTech SQL Problems](https://letsdatascience.com/problems?dataset=adtech_v1): Campaign, impression, click, and conversion analytics (Google, Meta, The Trade Desk)
- [Banking SQL Problems](https://letsdatascience.com/problems?dataset=banking_v1): Account, transaction, and loan analysis (JPMorgan, Goldman Sachs)
- [Fintech Trading Problems](https://letsdatascience.com/problems?dataset=fintech_trading_v1): Portfolio, order, and stock analysis (Robinhood, Schwab, Fidelity)
- [Health Claims Problems](https://letsdatascience.com/problems?dataset=health_claims_v1): Member, claim, and provider analysis (UnitedHealth, Cigna, Aetna)
- [Lodging Problems](https://letsdatascience.com/problems?dataset=lodging_v1): Property, booking, and review analysis (Airbnb, Booking.com, Marriott)
- [Logistics Problems](https://letsdatascience.com/problems?dataset=logistics_v1): Shipment, route, and warehouse optimization (FedEx, UPS, DHL)
- [Food Delivery Problems](https://letsdatascience.com/problems?dataset=marketplace_food_v1): Order, restaurant, and driver analytics (DoorDash, Uber Eats, Instacart)
- [Ride-Sharing Problems](https://letsdatascience.com/problems?dataset=marketplace_mobility_v1): Ride, driver, and passenger analysis (Uber, Lyft, Grab)
- [Payments Problems](https://letsdatascience.com/problems?dataset=payments_v1): Transaction, merchant, and dispute analysis (Stripe, PayPal, Square)
- [Real Estate Problems](https://letsdatascience.com/problems?dataset=real_estate_v1): Listing, agent, and transaction analysis (Zillow, Redfin, Compass)
- [Retail Problems](https://letsdatascience.com/problems?dataset=retail_v1): Product, order, and customer analysis (Amazon, Walmart, Shopify)
- [B2B SaaS Problems](https://letsdatascience.com/problems?dataset=saas_b2b_v1): Account, subscription, and usage analysis (Salesforce, HubSpot, Atlassian)
- [Social Network Problems](https://letsdatascience.com/problems?dataset=social_graph_v1): User, connection, and post analysis (LinkedIn, Twitter/X, Meta)
- [Streaming Media Problems](https://letsdatascience.com/problems?dataset=streaming_media_v1): User, content, and session analysis (Netflix, Spotify, YouTube)
- [Telecom Problems](https://letsdatascience.com/problems?dataset=telecom_isp_v1): Subscriber, plan, and network analysis (AT&T, Verizon, T-Mobile)

## Interactive Courses
The catalog has 13 active courses: 6 free courses and 7 Pro courses. Module 1 of every Pro course is free; Modules 2+ require a Pro subscription. All courses run code in-browser (Pyodide / sql.js / PGlite) with animated visualizations.
- [Learn Hub](https://letsdatascience.com/learn): All interactive courses
- [Full course syllabi (llms-full.txt)](https://letsdatascience.com/llms-full.txt): module-by-module concept outline of every course (topics + sections)
- [SQL Fundamentals](https://letsdatascience.com/learn/sql-fundamentals): SELECT, WHERE, GROUP BY, JOINs with animated visualizations (free)
- [SQL Mastery](https://letsdatascience.com/learn/sql-mastery): CASE, window functions (ROW_NUMBER, RANK, LAG/LEAD), CTEs, subqueries (free)
- [SQL Window Functions](https://letsdatascience.com/learn/sql-window-functions): OVER, PARTITION BY, ranking, ROWS/RANGE frames, LAG/LEAD, multi-dialect quirks, performance (Pro — Module 1 free)
- [Python Fundamentals](https://letsdatascience.com/learn/python-fundamentals): Variables, data structures, functions, OOP, error handling (free)
- [Pandas Fundamentals](https://letsdatascience.com/learn/pandas-fundamentals): DataFrames, selection, groupby, joins, reshaping, time series (free)
- [Statistics Foundations](https://letsdatascience.com/learn/statistics): Descriptive stats, distributions, spread & variability, skewness (free)
- [Probability for Data Scientists](https://letsdatascience.com/learn/probability): Conditional probability, random variables, distributions, Bayes, joint distributions, LLN & CLT (Pro — Module 1 free)
- [Machine Learning Fundamentals](https://letsdatascience.com/learn/ml-fundamentals): Linear & logistic regression, regularization, classification, metrics, cross-validation, sklearn pipelines (Pro — Module 1 free)
- [A/B Testing & Experimentation](https://letsdatascience.com/learn/ab-testing): Causal inference, hypotheses & OEC, power, randomization & SRM, CUPED, sequential testing, multi-armed bandits (Pro — Module 1 free)
- [LLM Foundations](https://letsdatascience.com/learn/llm-foundations): Tokenization, embeddings & RoPE, attention, the transformer block, training, inference/decoding, post-training (SFT/DPO/GRPO), interpretability (free)
- [Building RAG Systems & Vector Search](https://letsdatascience.com/learn/rag-vector-search): Retrieval, embeddings, chunking, hybrid search, vector indexes, reranking, grounding, citations, and RAG evaluation (Pro — Module 1 free)
- [Building AI Agents](https://letsdatascience.com/learn/building-ai-agents): Agent loops, tool use, structured outputs, planning, reflection, memory, multi-agent systems, evaluation, and guardrails (Pro — Module 1 free)
- [AI Evals: Test, Measure & Ship LLM Apps](https://letsdatascience.com/learn/ai-evals): Error analysis, deterministic and semantic scorers, LLM-as-judge alignment, confidence intervals, regression gates, and production evals (Pro — Module 1 free)

## Quick Recall
- [Quick Recall Hub](https://letsdatascience.com/quick-recall): Interview flashcards and SQL exercises — free, no signup
- [Interview Flashcards](https://letsdatascience.com/quick-recall/setup): 496 cards across SQL, Python, Statistics, ML, and LLMs
- [SQL Recall](https://letsdatascience.com/quick-recall/sql-recall): 33 lessons + 71 interactive SQL exercises across 11 topics

## Blog
- [Blog](https://letsdatascience.com/blog): Deep-dive articles with interactive code playgrounds and audio versions
- [System Design](https://letsdatascience.com/blog/system-design): ML system architecture and design patterns
- [Machine Learning](https://letsdatascience.com/blog/machine-learning): Algorithms, evaluation, feature engineering
- [Programming](https://letsdatascience.com/blog/programming): Python, SQL, and data engineering tutorials
- [Data](https://letsdatascience.com/blog/data): Analysis, visualization, and engineering
- [News](https://letsdatascience.com/blog/news): AI industry analysis and commentary

## AI & Data Science News
- [News Feed](https://letsdatascience.com/news): Real-time AI news with relevance scoring (1-10) and daily/weekly audio briefs
- [AI News Games](https://letsdatascience.com/news/games): Free daily AI news games with a free account — a new puzzle every day at 6 AM ET built from the last 24 hours of AI news, with saved scores and streaks
- [AI News Quiz](https://letsdatascience.com/news/games/quiz): Daily five-question quiz built from real AI headlines and figures from the last 24 hours, with links back to each story
- [Missing Word](https://letsdatascience.com/news/games/missing-word): Daily word game — guess the word removed from a real AI headline in three tries, with letter hints
- [AI Crossword](https://letsdatascience.com/news/games/crossword): Weekly mini crossword built each Monday from the words in that week's AI news, with approachable clues for general readers
- [Games Leaderboard](https://letsdatascience.com/news/games/leaderboard): Weekly, monthly, and all-time ranks across all games — points for correct answers, total time as the tiebreaker
- [AI News Topic Hubs](https://letsdatascience.com/news/topic): Live topic directory for OpenAI, Anthropic, Google AI, Grok/xAI, DeepSeek, NVIDIA, AI agents, infrastructure, policy, funding, and research coverage
- [Current News Index](https://letsdatascience.com/llms-news.txt): Fresh high-value AI news index for LLM retrieval, including recent articles and priority topic hubs
- [RSS Feed](https://letsdatascience.com/feed.xml): High-value recent news with descriptions, content, source links, images, and publication dates
- [Google News Sitemap](https://letsdatascience.com/news-sitemap.xml): Google News discovery sitemap for recent eligible articles
- [OpenAI News](https://letsdatascience.com/news/topic/openai): OpenAI, ChatGPT, GPT models, Sora, enterprise, funding, and policy coverage
- [Anthropic News](https://letsdatascience.com/news/topic/anthropic): Anthropic, Claude, AI safety, research, partnerships, and funding coverage
- [NVIDIA News](https://letsdatascience.com/news/topic/nvidia): NVIDIA GPUs, CUDA, AI platforms, data center wins, and earnings coverage
- [AI Agents News](https://letsdatascience.com/news/topic/ai-agents): Agent builders, frameworks, tool use, planning, and enterprise deployments
- [Agentic AI News](https://letsdatascience.com/news/topic/agentic-ai): Autonomous agents, multi-agent frameworks, and production deployments
- [AI Evaluation News](https://letsdatascience.com/news/topic/evaluation): Benchmarks, model evaluation, red-teaming, safety tests, and measurement updates
- [AI Infrastructure News](https://letsdatascience.com/news/topic/ai-infrastructure): Compute, GPUs, inference platforms, clouds, and AI infrastructure supply chain
- [AI Policy News](https://letsdatascience.com/news/topic/ai-policy): Regulation, government action, standards, enforcement, and public-sector AI decisions
- [AI Funding News](https://letsdatascience.com/news/topic/funding): Startup rounds, acquisitions, investors, valuations, and strategic financing
- [AI Research News](https://letsdatascience.com/news/topic/ai-research): Research papers, lab releases, benchmark movement, methods, and technical breakthroughs

## Optional
- [Pricing](https://letsdatascience.com/pricing): Pro subscription — $9.99/mo or $79.99/yr (unlocks all Pro course modules)
- [Privacy Policy](https://letsdatascience.com/privacy): Data handling practices
- [Terms of Service](https://letsdatascience.com/terms): Usage terms