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• SQL 50
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📚 LeetCode SQL Solutions in PostgreSQL

A collection of LeetCode solutions in SQL using PostgreSQL. Includes:

• Easy/Medium/Hard solutions
• Optimized queries

🔹 Features:

• Clean, formatted SQL code
• Use of PostgreSQL-specific functions
• Parsing complex queries
• Regular updates

Useful for preparing for technical interviews and improving your SQL skills.

• 1757. Recyclable and Low Fat Products
• 584. Find Customer Referee
• 595. Big Countries
• 1148. Article Views I
• 1683. Invalid Tweets

• 1378. Replace Employee ID With The Unique Identifier
• 1068. Product Sales Analysis I
• 1581. Customer Who Visited but Did Not Make Any Transactions
• 197. Rising Temperature
• 1661. Average Time of Process per Machine
• 577. Employee Bonus
• 1280. Students and Examinations
• 570. Managers with at Least 5 Direct Reports
• 1934. Confirmation Rate

• 620. Not Boring Movies
• 1251. Average Selling Price
• 1075. Project Employees I
• 1633. Percentage of Users Attended a Contest
• 1211. Queries Quality and Percentage
• 1193. Monthly Transactions I
• 1174. Immediate Food Delivery II
• 550. Game Play Analysis IV

• 2356. Number of Unique Subjects Taught by Each Teacher
• 1141. User Activity for the Past 30 Days I
• 1070. Product Sales Analysis III
• 596. Classes With at Least 5 Students
• 1729. Find Followers Count
• 619. Biggest Single Number
• 1045. Customers Who Bought All Products

• 1731. The Number of Employees Which Report to Each Employee
• 1789. Primary Department for Each Employee
• 610. Triangle Judgement
• 180. Consecutive Numbers
• 1164. Product Price at a Given Date
• 1204. Last Person to Fit in the Bus
• 1907. Count Salary Categories

• 1978. Employees Whose Manager Left the Company
• 626. Exchange Seats
• 1321. Restaurant Growth
• 1341. Movie Rating
• 602. Friend Requests II: Who Has the Most Friends
• 585. Investments in 2016
• 185. Department Top Three Salaries

• 1667. Fix Names in a Table
• 1527. Patients With a Condition
• 176. Second Highest Salary
• 1484. Group Sold Products By The Date
• 196. Delete Duplicate Emails
• 1327. List the Products Ordered in a Period
• 1517. Find Users With Valid E-Mails

1. Easy
   • 175. Combine Two Tables
   • 181. Employees Earning More Than Their Managers
   • 182. Duplicate Emails
   • 183. Customers Who Never Order
   • 196. Delete Duplicate Emails
   • 197. Rising Temperature
   • 511. Game Play Analysis 1
   • 577. Employee Bonus
   • 584. Find Customer Referee
   • 586. Customer Placing the Largest Number of Orders
   • 595. Big Countries
   • 596. Classes With at Least 5 Students
   • 607. Sales Person
   • 610. Triangle Judgement
   • 619. Biggest Single Number
   • 620. Not Boring Movies
   • 627. Swap Salary
   • 1050. Actors and Directors Who Cooperated At Least Three Times
   • 1068. Product Sales Analysis I
   • 1075. Project Employees I
   • 1084. Sales Analysis III
   • 1141. User Activity for the Past 30 Days I
   • 1148. Article Views I
   • 1179. Reformat Department Table
   • 1211. Queries Quality and Percentage
   • 1251. Average Selling Price
   • 1280. Students and Examinations
   • 1327. List the Products Ordered in a Period
   • 1378. Replace Employee ID With The Unique Identifier
   • 1407. Top Travellers
   • 1484. Group Sold Products By The Date
   • 1517. Find Users With Valid E-Mails
   • 1527. Patients With a Condition
   • 1581. Customer Who Visited but Did Not Make Any Transactions
   • 1587. Bank Account Summary II
   • 1633. Percentage of Users Attended a Contest
   • 1661. Average Time of Process per Machine
   • 1667. Fix Names in a Table
   • 1683. Invalid Tweets
   • 1693. Daily Leads and Partners
   • 1729. Find Followers Count
   • 1731. The Number of Employees Which Report to Each Employee
   • 1741. Find Total Time Spent by Each Employee
   • 1757. Recyclable and Low Fat Products
   • 1789. Primary Department for Each Employee
   • 1795. Rearrange Products Table
   • 1873. Calculate Special Bonus
   • 1890. The Latest Login in 2020
   • 1965. Employees With Missing Information
   • 1978. Employees Whose Manager Left the Company
   • 2356. Number of Unique Subjects Taught by Each Teacher
   • 3436. Find Valid Emails
   • 3465. Find Products with Valid Serial Numbers
   • 3570. Find Books with No Available Copies
2. Medium
   • 176. Second Highest Salary
   • 177. Nth Highest Salary
   • 180. Consecutive Numbers
   • 184. Department Highest Salary
   • 550. Game Play Analysis IV
   • 570. Managers with at Least 5 Direct Reports
   • 585. Investments in 2016
   • 602. Friend Requests II: Who Has the Most Friends
   • 608. Tree Node
   • 626. Exchange Seats
   • 1045. Customers Who Bought All Products
   • 1070. Product Sales Analysis III
   • 1158. Market Analysis 1
   • 1164. Product Price at a Given Date
   • 1174. Immediate Food Delivery II
   • 1193. Monthly Transactions I
   • 1204. Last Person to Fit in the Bus
   • 1321. Restaurant Growth
   • 1341. Movie Rating
   • 1393. Capital Gain/Loss
   • 1907. Count Salary Categories
   • 1934. Confirmation Rate
   • 3220. Odd and Even Transactions
   • 3421. Find Students Who Improved
   • 3475. DNA Pattern Recognition
   • 3497. Analyze Subscription Conversion
   • 3521. Find Product Recommendation Pairs
   • 3564. Seasonal Sales Analysis
   • 3580. Find Consistently Improving Employees
   • 3586. Find COVID Recovery Patients
   • 3601. Find Drivers with Improved Fuel Efficiency
   • 3611. Find Overbooked Employees
3. Hard
   • 185. Department Top Three Salaries
   • 262. Trips and Users
   • 601. Human Traffic of Stadium
   • 3374. First Letter Capitalization II
   • 3451. Find Invalid IP Addresses
   • 3482. Analyze Organization Hierarchy
   • 3554. Find Category Recommendation Pairs

Style guide for contributors:

1. Add description to all tasks from Leetcode.
2. Name file pattern: xxx.Task name.sql
3. All keywords must be uppercase.
4. For every task create new branch with pattern: task/task-id -> make PR to main.

Have a good contributing!

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