LeetCode SQL 50 Solutions

🚀 A comprehensive collection of solutions to the top 50 SQL problems on LeetCode. Each solution is written with clear explanations and best practices to help users master SQL queries, including SELECT, JOIN, GROUP BY, HAVING, window functions, and more. Perfect for beginners and those preparing for SQL interviews!

Features:

• 📝 Well-documented SQL scripts for all 50 problems.
• 📚 Easy-to-follow explanations for each query.
• ✅ Solutions optimized for readability and efficiency.
• 🎯 Covers beginner to intermediate SQL topics.

Table of Contents

1. Introduction
2. Problem List
3. Solutions
4. How to Use
5. Contributing

Introduction

This repository contains solutions to the top 50 SQL problems on LeetCode, ranging from basic SELECT queries to more advanced JOINs and window functions. The solutions are designed to be beginner-friendly, with clear explanations of each concept and solution.

Whether you're preparing for SQL-based technical interviews or just want to improve your SQL skills, this repository will help you understand the most common SQL challenges and how to approach them efficiently.

Problem List

Here is the list of the top 50 SQL problems solved in this repository:

1. Combine Two Tables
2. Second Highest Salary
3. Rank Scores
4. Reorder Data in Log Files
5. Employees Earning More Than Their Managers
6. Department Highest Salary
7. Employees With a High Salary
8. Deleting Records
9. Patching Array
10. Weather Observation Station 1
11. Weather Observation Station 2
12. Weather Observation Station 3
13. Consecutive Numbers
14. Not Boring Movies
15. Average Salary Excluding the Minimum and Maximum Salary
16. Employee Bonus
17. Find the Developer's Name
18. Total Sales Amount by Region
19. Biggest Triangle Area
20. Students and Examinations
21. Duplicate Emails
22. Find All Duplicates in an Array
23. Group Anagrams
24. Most Frequent Subtree Sum
25. Intersection of Two Arrays
26. Subdomain Visit Count
27. Unique Email Addresses
28. Find the City With the Smallest Number of Neighbors at a Threshold Distance
29. Count Number of Nice Subarrays
30. Find the Winner of an Array Game
31. Sum of Unique Elements
32. Rank of a Stream
33. Reverse Rows in a Matrix
34. Delete Duplicate Emails
35. Count Substrings with Only One Distinct Letter
36. Count Primes
37. Find the City With the Smallest Number of Neighbors at a Threshold Distance
38. Basic Calculator
39. First Unique Character in a String
40. Merge Intervals
41. Palindrome Number
42. Longest Substring Without Repeating Characters
43. Valid Anagram
44. Symmetric Tree
45. Path Sum II
46. Lowest Common Ancestor of a Binary Tree
47. Linked List Cycle
48. Palindrome Linked List
49. Single Number
50. Intersection of Two Arrays II

Solutions

Each SQL problem has a corresponding solution located in a separate file. You can explore the solutions by browsing the repository or by following the table of contents above. Every solution comes with:

How to Use

1. Clone the repository

2. Navigate to the directory containing the SQL files for each problem.

3. Open the relevant SQL file and study the solution and explanations provided.

4. You can execute the SQL queries on your local SQL environment or platforms like LeetCode to test and practice.

Contributing

If you'd like to contribute to this repository, feel free to submit pull requests. Whether it's fixing a bug, optimizing a solution, or adding an additional explanation, your contributions are welcome!

To contribute:

1. Fork this repository.

2. Create a new branch for your changes.

3. Make the necessary changes.

4. Submit a pull request with a detailed description of your changes.

Happy Coding! ✨