Question 1

What is the SQL Visualizer?

Accepted Answer

The SQL Visualizer is a step-by-step query execution tool that shows exactly how your SQL query runs — how JOINs match rows, how WHERE filters data, how GROUP BY aggregates results, and how ORDER BY sorts output. It runs directly in your browser against real datasets.

Question 2

What is the Python Visualizer?

Accepted Answer

The Python Visualizer shows pandas DataFrame transformations step by step — see how merge, groupby, filter, and reshape operations change your data at each stage. It runs via Pyodide (Python compiled to WebAssembly) entirely in your browser.

Question 3

How does the AI Mentor work?

Accepted Answer

The LDS Mentor offers two modes: Learn Mode uses Socratic guidance with escalating hints to help you think through problems independently. Interview Mode gives you direct patterns, code skeletons, and strategies at interview speed — ideal for timed practice.

Question 4

Do I need to install anything to practice?

Accepted Answer

No. All SQL and Python problems run entirely in your browser using SQLite (via sql.js WebAssembly) and Python (via Pyodide). There is nothing to install — just open a problem and start coding.

Question 5

What datasets are the problems based on?

Accepted Answer

Problems use 15 real-world industry datasets spanning fintech, e-commerce, healthcare, adtech, logistics, banking, SaaS, telecom, streaming media, real estate, social networks, food delivery, ride-sharing, lodging, and payments.

Question 6

Are there solutions for every problem?

Accepted Answer

Yes. Every problem includes a detailed solution with code (both SQLite and PostgreSQL dialects for SQL problems), a step-by-step explanation of the approach, and tips on how to explain it in an interview setting.

SQL & Python Practice Problems with Step-by-Step Visualizer & AI Mentor