📊 LeetCode SQL Practice

Daily SQL problem-solving journey — building strong SQL fundamentals through LeetCode, one problem at a time.

Language: MySQL Study Plan: SQL 50 Progress: 12 / 50 ✅

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📁 Repository Structure

SQL/
├── 197_Rising_Temperature/
│   ├── README.md
│   └── solution.sql
├── 577_Employee_Bonus/
│   ├── README.md
│   └── solution.sql
├── 584_Find_Customer_Referee/
│   ├── README.md
│   └── solution.sql
├── 595_Big_Countries/
│   ├── README.md
│   └── solution.sql
├── 1068_Product_Sales_Analysis_I/
│   ├── README.md
│   └── solution.sql
├── 1148_Article_Views_I/
│   ├── README.md
│   └── solution.sql
├── 1280_Students_and_Examinations/
│   ├── README.md
│   └── solution.sql
├── 1378_Replace_Employee_ID_With_The_Unique_Identifier/
│   ├── README.md
│   └── solution.sql
├── 1581_Customer_Who_Visited_but_Did_Not_Make_Any_Transactions/
│   ├── README.md
│   └── solution.sql
├── 1661_Average_Time_of_Process_per_Machine/
│   ├── README.md
│   └── solution.sql
├── 1683_Invalid_Tweets/
│   ├── README.md
│   └── solution.sql
└── 1757_Recyclable_and_Low_Fat_Products/
    ├── README.md
    └── solution.sql

Each problem folder contains:

• 📘 README.md — Problem summary, explanation, concepts, and key learnings
• 💻 solution.sql — Accepted MySQL solution

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📈 Progress

#	Problem	Difficulty	Concepts
1757	Recyclable and Low Fat Products	🟢 Easy	WHERE, AND
584	Find Customer Referee	🟢 Easy	NULL, IS NULL, OR
595	Big Countries	🟢 Easy	WHERE, OR
1148	Article Views I	🟢 Easy	DISTINCT, ORDER BY
1683	Invalid Tweets	🟢 Easy	LENGTH()
1378	Replace Employee ID With The Unique Identifier	🟢 Easy	LEFT JOIN
1068	Product Sales Analysis I	🟢 Easy	INNER JOIN
1581	Customer Who Visited but Did Not Make Any Transactions	🟢 Easy	LEFT JOIN, IS NULL, GROUP BY
1661	Average Time of Process per Machine	🟢 Easy	SELF JOIN, GROUP BY, AVG(), ROUND()
197	Rising Temperature	🟢 Easy	SELF JOIN, DATEDIFF()
577	Employee Bonus	🟢 Easy	LEFT JOIN, IS NULL, OR
1280	Students and Examinations	🟢 Easy	CROSS JOIN, LEFT JOIN, GROUP BY, COUNT()

This table is updated as I solve more problems.

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🎯 Goal

Build strong SQL fundamentals by consistently solving problems covering filtering, joins, aggregation, subqueries, and advanced SQL concepts.

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🧠 Topics

Covered so far:

• SELECT & WHERE
• AND / OR
• NULL Handling
• INNER JOIN & LEFT JOIN
• CROSS JOIN
• Self-Joins
• Multi-column JOIN conditions
• Aggregate Functions (AVG, ROUND, DISTINCT, COUNT)
• GROUP BY
• DATEDIFF()

Up next:

• HAVING
• Subqueries
• CTEs
• Window Functions