📊 LeetCode SQL 50 — Study Plan Solutions

Solutions to LeetCode's SQL 50 study plan, solved daily and pushed automatically via LeetHub.

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🚀 About

This repository tracks my progress through LeetCode's SQL 50 study plan — a curated set of 50 problems covering the core SQL concepts needed for interviews: joins, subqueries, aggregation, window functions, and string/date manipulation.

• 🗓️ Solving daily
• 🔁 Auto-synced from LeetCode via LeetHub
• 🎯 Goal: complete all 50 problems

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📈 Progress

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🗂️ Problems

#	Title	Difficulty	Topics	Solution
1	Recyclable and Low Fat Products	Easy	Filtering	Solution
2	Find Customer Referee	Easy	Filtering
3	Big Countries	Easy	Filtering
4	Article Views I	Easy	Filtering
5	Invalid Tweets	Easy	Filtering
6	Replace Employee ID With The Unique Identifier	Easy	Joins
7	Product Sales Analysis I	Easy	Joins
8	Customer Who Visited but Did Not Make Any Transactions	Easy	Joins
9	Rising Temperature	Easy	Joins
10	Average Time of Process per Machine	Easy	Joins
11	Employee Bonus	Easy	Joins
12	Students and Examinations	Easy	Joins
13	Managers with at Least 5 Direct Reports	Medium	Joins
14	Confirmation Rate	Easy	Joins
15	Not Boring Movies	Easy	Basic Aggregation
16	Average Selling Price	Easy	Basic Aggregation
17	Project Employees I	Easy	Basic Aggregation
18	Percentage of Users Attended a Contest	Easy	Basic Aggregation
19	Queries Quality and Percentage	Easy	Basic Aggregation
20	Monthly Transactions I	Medium	Basic Aggregation
21	Immediate Food Delivery II	Medium	Basic Aggregation
22	Game Play Analysis IV	Medium	Basic Aggregation
23	Number of Unique Subjects Taught by Each Teacher	Easy	Sorting & Grouping
24	User Activity for the Past 30 Days I	Easy	Sorting & Grouping
25	Product Sales Analysis III	Medium	Sorting & Grouping
26	Classes More Than 5 Students	Easy	Sorting & Grouping
27	Find Followers Count	Easy	Sorting & Grouping
28	Biggest Single Number	Easy	Sorting & Grouping
29	Customers Who Bought All Products	Medium	Sorting & Grouping
30	The Number of Employees Which Report to Each Employee	Easy	Advanced Select & JOIN
31	Primary Department for Each Employee	Easy	Advanced Select & JOIN
32	Triangle Judgement	Easy	Advanced Select & JOIN
33	Consecutive Numbers	Medium	Subqueries
34	Product Price at a Given Date	Medium	Subqueries
35	Last Person to Fit in the Bus	Medium	Subqueries
36	Count Salary Categories	Medium	Subqueries
37	Second Highest Salary	Medium	Advanced String Functions / Regex / Clause
38	Group Sold Products By The Date	Easy	Advanced String Functions / Regex / Clause
39	List the Products Ordered in a Period	Easy	Advanced String Functions / Regex / Clause
40	Find Users With Valid E-Mails	Easy	Advanced String Functions / Regex / Clause
41	Patients With a Condition	Easy	Advanced String Functions / Regex / Clause
42	Delete Duplicate Emails	Easy	Advanced String Functions / Regex / Clause
43	Rearrange Products Table	Easy	Advanced String Functions / Regex / Clause
44	Fix Names in a Table	Easy	Advanced String Functions / Regex / Clause
45	Nth Highest Salary	Medium	Advanced String Functions / Regex / Clause
46	Employees Earning More Than Their Managers	Easy	Advanced String Functions / Regex / Clause
47	Duplicate Emails	Easy	Advanced String Functions / Regex / Clause
48	Customers Who Never Order	Easy	Advanced String Functions / Regex / Clause
49	Department Highest Salary	Medium	Advanced String Functions / Regex / Clause
50	Exchange Seats	Medium	Advanced String Functions / Regex / Clause

✅ = solved · Solution column links to the folder once pushed by LeetHub.

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🛠️ Tech

• Language: SQL (MySQL dialect, as used by LeetCode)
• Sync tool: LeetHub 2.0

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📌 Notes

• Each problem folder is auto-created by LeetHub and contains the accepted solution along with the problem statement.
• This repo is for personal practice and tracking — solutions may not always be the most optimal, but reflect my learning process.

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⭐ If you're also grinding SQL 50, feel free to fork this and track your own progress!

LeetCode Topics

Database

0176-second-highest-salary
0570-managers-with-at-least-5-direct-reports
0595-big-countries
1148-article-views-i
1484-group-sold-products-by-the-date
1527-patients-with-a-condition
1667-fix-names-in-a-table
1683-invalid-tweets