SQL Practice & Analytics Patterns

This repo is my SQL training log + reusable analytics templates. It includes:

• LeetCode solutions (drills)
• Real-world analytics patterns (window functions, cohorts, funnels, reconciliation)
• Mini-projects (e.g., Olist growth analysis)

Why this repo

I don't want SQL to be "query writing". I want it to be decision-ready analytics: correct grain, clean population rules, and validation checks.

Structure

• /leetcode — interview-style problems
• /patterns — reusable templates with pitfalls + validation
• /projects — end-to-end case studies

Highlighted patterns

• Cohort retention (month_index)
• New vs returning buyers tagging
• Time-series smoothing (MA7)
• Revenue reconciliation (gross → net bridge)
• Deduplication strategies (payment/event retries)

Notes

Each solution includes:

• problem statement (short)
• approach
• SQL
• common pitfalls / validation checks