🗃️ SQL-50 — LeetCode SQL Problem Solutions

Solving 50 SQL problems on LeetCode — from basic JOINs to advanced window functions.
Clean, well-commented solutions organised by concept. Updated daily.

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📌 Why This Repo?

SQL is tested in almost every Data Analyst, ML Engineer, and Backend role interview.
This repo is my structured practice log — each solution includes the problem link, approach, and clean query.

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✅ Problems Solved

#	Problem	Difficulty	Concept	Solution
1	Combine Two Tables	🟢 Easy	LEFT JOIN	View
2	Second Highest Salary	🟡 Medium	LIMIT + OFFSET	View
3	Nth Highest Salary	🟡 Medium	Stored Function	View
4	Rank Scores	🟡 Medium	DENSE_RANK	View
5	Consecutive Numbers	🟡 Medium	Self JOIN	View

🔄 More problems being added daily — check back soon!

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📚 Concepts Covered (Roadmap)

✅ JOINs          → INNER, LEFT, RIGHT, SELF JOIN
✅ Window Funcs   → RANK, DENSE_RANK, ROW_NUMBER
✅ Subqueries     → Scalar, Correlated, IN / NOT IN
🔲 Aggregations   → GROUP BY, HAVING, COUNT, SUM
🔲 String Funcs   → CONCAT, SUBSTRING, LIKE
🔲 Date Funcs     → DATEDIFF, DATE_FORMAT, NOW()
🔲 CTEs           → WITH clause, recursive queries
🔲 NULL Handling  → IFNULL, COALESCE, IS NULL

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🛠️ Tech Stack

• Database: MySQL (LeetCode environment)
• Tools: LeetCode SQL Editor, VS Code
• Language: Standard SQL with MySQL-specific functions

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📁 Repo Structure

sql-50/
├── Combine Two Tables          # LEFT JOIN basics
├── Second Highest Salary       # LIMIT + OFFSET / subquery
├── Nth Highest Salary          # Stored function + LIMIT
├── Rank Scores                 # DENSE_RANK window function
├── Consecutive Numbers         # Self JOIN technique
└── README.md

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🚀 How to Use

1. Click any problem file to see the SQL solution
2. Each file has the query + a short comment explaining the approach
3. Try solving it yourself first on LeetCode before reading!

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👩‍💻 About Me

Madhura Bhat — B.Tech AI & Data Science | Actively seeking Data/ML/GenAI roles

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⭐ If this helped you, consider starring the repo!