LeetCode SQL 50

This repository contains solutions to 50 SQL challenges from LeetCode (https://leetcode.com/studyplan/top-sql-50/). Organized by topic, with clean SQL code.

Nº	Title	Difficulty	Topic	Solution
1	Recyclable and Low Fat Products	Easy	Select	SQL
2	Find Customer Referee	Easy	Select	SQL
3	Big Countries	Easy	Select	SQL
4	Article Views I	Easy	Select	SQL
5	Invalid Tweets	Easy	Select	SQL
6	Replace Employee ID With The Unique Identifier (Basic Joins)	Easy	Basic Joins	SQL
7	Product Sales Analysis I	Easy	Basic Joins	SQL
8	Customer Who Visited but Did Not Make Any Transactions	Easy	Basic Joins	SQL
9	Rising Temperature	Easy	Basic Joins	SQL
10	Average Time of Process per Machine	Easy	Basic Joins	SQL
11	Employee Bonus	Easy	Basic Joins	SQL
12	Students and Examinations	Easy	Basic Joins	SQL
13	Managers with at Least 5 Direct Reports	Medium	Basic Joins	SQL
14	Confirmation Rate	Medium	Basic Joins	SQL
15	Not Boring Movies	Easy	Basic Aggregate Functions	SQL
16	Average Selling Price	Easy	Basic Aggregate Functions	SQL
17	Project Employees I	Easy	Basic Aggregate Functions	SQL
18	Percentage of Users Attended a Contest	Easy	Basic Aggregate Functions	SQL
19	Queries Quality and Percentage	Easy	Basic Aggregate Functions	SQL
20	Monthly Transactions I	Medium	Basic Aggregate Functions	SQL
21	Immediate Food Delivery II	Medium	Basic Aggregate Functions	SQL
22	Game Play Analysis IV	Medium	Basic Aggregate Functions	SQL
23	Number of Unique Subjects Taught by Each Teacher	Easy	Sorting and Grouping	SQL
24	User Activity for the Past 30 Days I	Easy	Sorting and Grouping	SQL
25	Product Sales Analysis III	Medium	Sorting and Grouping	SQL
26	Classes With at Least 5 Students	Easy	Sorting and Grouping	SQL
27	Find Followers Count	Easy	Sorting and Grouping	SQL
28	Biggest Single Number	Easy	Sorting and Grouping	SQL
29	Customers Who Bought All Products	Medium	Sorting and Grouping	SQL
30	The Number of Employees Which Report to Each Employee	Easy	Advanced Select and Joins	SQL
31	Primary Department for Each Employee	Easy	Advanced Select and Joins	SQL
32	Triangle Judgement	Easy	Advanced Select and Joins	SQL
33	Consecutive Numbers	Medium	Advanced Select and Joins	SQL
34	Product Price at a Given Date	Medium	Advanced Select and Joins	SQL
35	Last Person to Fit in the Bus	Medium	Advanced Select and Joins	SQL
36	Count Salary Categories	Medium	Advanced Select and Joins	SQL
37	Employees Whose Manager Left the Company	Easy	Subqueries	SQL
38	Exchange Seats	Medium	Subqueries	SQL
39	Movie Rating	Medium	Subqueries	SQL
40	Restaurant Growth	Medium	Subqueries	SQL
41	Friend Requests II: Who Has the Most Friends	Medium	Subqueries	SQL
42	Investments in 2016	Medium	Subqueries	SQL
43	Department Top Three Salaries	Hard	Subqueries	SQL
44	Fix Names in a Table	Easy	Advanced Functions	SQL
45	Patients With a Condition	Easy	Advanced Functions	SQL
46	Delete Duplicate Emails	Easy	Advanced Functions	SQL
47	Second Highest Salary	Medium	Advanced Functions	SQL
48	Group Sold Products By The Date	Easy	Advanced Functions	SQL
49	List the Products Ordered in a Period	Easy	Advanced Functions	SQL
50	Find Users With Valid E-Mails	Easy	Advanced Functions	SQL