This repository contains my daily solutions for LeetCode's Top 50 SQL problems. Each day, I solve one problem, write the SQL query, and add notes for better understanding.
📅 Start Date: June 20, 2025 📅 End Date: August 23, 2025 🎯 Goal: Complete all 50 problems
Update: It was an amazing journey. After completing this challenge, I feel much more confident in my SQL skills. This problem set was thoughtfully designed and really helped me strengthen my understanding. I’m proud of the consistency and effort I put into completing all 50 problems, and I’m excited to take on even more challenges in the future! 💪✨
| Day | Problem Title | Solution File |
|---|---|---|
| 01 | Recyclable and Low Fat Products | SQL |
| 02 | Find Customer Referee | SQL |
| 03 | Big Countries | SQL |
| 04 | Article Views I | SQL |
| 05 | Invalid Tweets | SQL |
| 06 | Replace Employee_id With The Unique Identifier | SQL |
| 07 | Product Sales Analysis I | SQL |
| 08 | Customer Who Visited But Did Not Make Any Transactions | SQL |
| 09 | Rising Temperature | SQL |
| 10 | Average Time of Process Per Machine | SQL |
| 11 | Employee Bonus | SQL |
| 12 | Students and Examinations | SQL |
| 13 | Managers With At Least 5 Direct Reports | SQL |
| 14 | Confirmation Rate | SQL |
| 15 | Not Boring Movies | SQL |
| 16 | Average Selling Price | SQL |
| 17 | Project Employees I | SQL |
| 18 | Project Percentage Of Users Attended A Contest | SQL |
| 19 | Queries Quality and Percentage | SQL |
| 20 | Monthly Transactions I | SQL |
| 21 | Immediate Food Delivery II | SQL |
| 22 | Game Play Analysis IV | SQL |
| 23 | Number of Unique Subjects Taught by Each Teacher | SQL |
| 24 | User Activity for the Past 30 Days I | SQL |
| 25 | Product Sales Analysis III | SQL |
| 26 | Classes With at Least 5 Students | SQL |
| 27 | Find Followers Count | SQL |
| 28 | Biggest Single Number | SQL |
| 29 | Customers Who Bought All Products | SQL |
| 30 | The Number of Employees Which Report to Each Employee | SQL |
| 31 | Primary Department for Each Employee | SQL |
| 32 | Triangle Judgement | SQL |
| 33 | Consecutive Numbers | SQL |
| 34 | Product Price at a Given Date | SQL |
| 35 | Last Person to Fit in the Bus | SQL |
| 36 | Count Salary Categories | SQL |
| 37 | Employees Whose Manager Left the Company | SQL |
| 38 | Exchange Seats | SQL |
| 39 | Movie Rating | SQL |
| 40 | Restaurant Growth | SQL |
| 41 | Friend Requests II: Who Has the Most Friends | SQL |
| 42 | Investments In 2016 | SQL |
| 43 | Department Top Three Salaries | SQL |
| 44 | Fix Names In a Table | SQL |
| 45 | Patients With a Condition | SQL |
| 46 | Delete Duplicate Emails | SQL |
| 47 | Second Highest Salary | SQL |
| 48 | Group Sold Products By The Date | SQL |
| 49 | List the Products Ordered in a Period | SQL |
| 50 | Find Users With Valid E-Mails | SQL |