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SQL Data Analytics Portfolio

This repository showcases my SQL skills for Data Analyst roles, with a focus on solving real-world analytical and business problems.

Rather than emphasizing algorithmic difficulty, the queries in this project demonstrate how SQL is used for:

  • KPI reporting
  • Financial aggregation
  • User behavior analysis
  • Time-based trend analysis

🧠 Core SQL Skills

  • Multi-table JOINs and subqueries
  • Aggregation and KPI calculation
  • Window functions (ROW_NUMBER, RANK)
  • Time-based analysis (monthly metrics)
  • Translating business questions into SQL logic

📂 Project Files

  • MySQL.sql
    SQL solutions written in MySQL syntax

  • SQLServer.sql
    Equivalent solutions adapted for SQL Server (T-SQL)

  • explanation.md
    Business context and analytical explanation for selected queries

📊 Business-Oriented Case Examples

Monthly Transaction Analysis

Aggregates transaction counts and approved amounts by month and country.
Common real-world use cases:

  • Financial reporting
  • Operational dashboards
  • Management summaries

Capital Gain / Loss Calculation

Calculates profit and loss from buy and sell transaction records.
Common real-world use cases:

  • Trading PnL reports
  • Investment performance tracking

User Activity & Retention Analysis

Analyzes user behavior using window functions.
Common real-world use cases:

  • Product usage analysis
  • Retention and churn metrics

🛠 SQL Dialects

This project includes solutions in:

  • MySQL
  • SQL Server (T-SQL)

Queries are adapted to account for syntax differences such as date handling and conditional aggregation.

🎯 Why This Repository

This portfolio is designed to reflect how SQL is actually used in Data Analyst roles:

  • Queries prioritize readability and maintainability
  • Business logic is clearly documented
  • Solutions are interview-ready and explainable

📎 Notes

  • SQL files include comments describing the analytical purpose
  • Selected queries are explained in explanation.md
  • Problems are chosen to reflect common analytics scenarios

📁 Folder Structure

leetcode-sql-solutions-main/ │ ├─ README.md
├─ .gitignore ├─ .git ├─ .vscode/
│ ├─ 01_basic_select_join/ │ ├─ README.md │ ├─ 00175-combine-two-tables/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 00178-rank-scores/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 00181-employees-earning-more-than-their-managers/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 00570-managers-with-at-least-5-direct-reports/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ └─ 00620-not-boring-movies/ │ ├─ explanation.md │ ├─ MySQL.sql │ └─ SQLServer.sql │ ├─ 02_aggregation_groupby/ │ ├─ README.md │ ├─ 00176-second-highest-salary/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 01193-monthly-transactions-i/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 01211-queries-quality-and-percentage/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ └─ 01393-capital-gain-or-loss/ │ ├─ explanation.md │ ├─ MySQL.sql │ └─ SQLServer.sql │ ├─ 03_subquery_anti_join/ │ ├─ README.md │ └─ 00183-customers-who-never-order/ │ ├─ explanation.md │ ├─ MySQL.sql │ └─ SQLServer.sql │ ├─ 04_window_functions/ │ ├─ README.md │ ├─ 00184-department-highest-salary/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 00185-department-top-three-salaries/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 00550-game-play-analysis-iv/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ └─ 01141-user-activity/ │ ├─ explanation.md │ ├─ MySQL.sql │ └─ SQLServer.sql │ ├─ 05_time_series_analysis/ │ ├─ README.md │ ├─ 00197-rising-temperature/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 00511-game-play-analysis-i/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ ├─ 01174-immediate-food-delivery-ii/ │ │ ├─ explanation.md │ │ ├─ MySQL.sql │ │ └─ SQLServer.sql │ └─ 01321-restaurant-growth/ │ ├─ explanation.md │ ├─ MySQL.sql │ └─ SQLServer.sql