Welcome to my little corner where I document my solutions and thoughts for the LeetCode SQL 50 study plan.
This repo is all about learning, growing, and making SQL practice feel graceful and enjoyable ✨
- Solutions to all 50 SQL problems
- Written in both MySQL and MS SQL Server
- Notes that capture my thought process, tips, and lessons learned
- A personal reference to revisit before interviews
| Problem | Difficulty |
|---|---|
| Recyclable and Low Fat Products | Easy |
| Find Customer Referee | Easy |
| Big Countries | Easy |
| Article Views I | Easy |
| Invalid Tweets | Easy |
| Replace Employee ID With The Unique Identifier | Easy |
| Product Sales Analysis I | Easy |
| Customer Who Visited but Did Not Make Any Transactions | Easy |
| Rising Temperature | Easy |
| Average Time of Process per Machine | Easy |
| Employee Bonus | Easy |
| Students and Examinations | Easy |
| Managers with at Least 5 Direct Reports | Medium |
| Confirmation Rate | Medium |
| Not Boring Movies | Easy |
| Average Selling Price | Easy |
| Project Employees I | Easy |
| Percentage of Users Attended a Contest | Easy |
| Queries Quality and Percentage | Easy |
| Monthly Transactions I | Medium |
| Immediate Food Delivery II | Medium |
| Game Play Analysis IV | Medium |
| Number of Unique Subjects Taught by Each Teacher | Easy |
| User Activity for the Past 30 Days I | Easy |
| Product Sales Analysis III | Medium |
| Classes With at Least 5 Students | Easy |
| Find Followers Count | Easy |
| Biggest Single Number | Easy |
| Customers Who Bought All Products | Medium |
| The Number of Employees Which Report to Each Employee | Easy |
| Primary Department for Each Employee | Easy |
| Triangle Judgement | Easy |
| Consecutive Numbers | Medium |
| Product Price at a Given Date | Medium |
| Last Person to Fit in the Bus | Medium |
| Count Salary Categories | Medium |
| Employees Whose Manager Left the Company | Easy |
| Exchange Seats | Medium |
| Movie Rating | Medium |
| Restaurant Growth | Medium |
| Friend Requests II: Who Has the Most Friends | Medium |
| Investments in 2016 | Medium |
| Department Top Three Salaries | Hard |
| Fix Names in a Table | Easy |
| Patients With a Condition | Easy |
| Delete Duplicate Emails | Easy |
| Second Highest Salary | Medium |
| Group Sold Products By The Date | Easy |
| List the Products Ordered in a Period | Easy |
| Find Users With Valid E-Mails | Easy |
- To strengthen my SQL skills step by step
- To feel confident in technical interviews
- To build a soft & structured personal reference
The SQL 50 study plan is a curated set of SQL problems on LeetCode, starting from easy and moving to medium. It’s a perfect way to polish database skills and get interview-ready.
💖 Here’s to making learning SQL a little more beautiful, one query at a time.