Initial commit

Author: Ivanbyone

.gitattributes

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+*.sql linguist-language=PLpgSQL

.github/workflows/ci.yml

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+name: CI
+
+on: 
+  pull_request:
+    branches: [main, develop]
+
+jobs: 
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Lint SQL
+        run: |
+            pip install sqlfluff
+            sqlfluff lint leetcode/ --config .sqlfluff

.gitignore

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+# macOS
+.DS_Store
+
+# VS Code
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+
+# Ignore temporary files
+.tmp

.sqlfluff

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+[sqlfluff]
+dialect = postgres
+exclude_rules = LT01, CP02
+
+[sqlfluff:rules]
+keywords_capitalisation_policy = upper
+max_line_length = 100

LICENSE

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+MIT License
+
+Copyright (c) 2025 Ivan Boyko <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# Leetcode (PostgreSQL)
+
+[![MIT licensed](https://img.shields.io/badge/License-MIT-yellow.svg)](./LICENSE)
+[![CI](https://github.com/ivanbyone/hookify/actions/workflows/ci.yml/badge.svg)](https://github.com/Ivanbyone/leetcode-sql//actions)
+
+## Description
+
+📚 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.
+
+### Contributing
+
+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-name -> make PR to main.
+
+Have a good contributing! 
+
+## Task List
+
+1. [Easy](./leetcode/easy/)
+    - [182. Duplicate Emails](./leetcode/easy/182.%20Duplicate%20Emails.sql)
+    - [175. Combine Two Tables](./leetcode//easy/175.%20Combine%20Two%20Tables.sql)
+    - [183. Customers Who Never Order](./leetcode/easy/183.%20Customers%20Who%20Never%20Order.sql)
+    - [511. Game Play Analysis 1](./leetcode/easy/511.%20Game%20Play%20Analysis%201.sql)
+    - [595. Big Countries](./leetcode/easy/595.%20Big%20Countries.sql)
+
+## License
+
+Check out LICENSE [page](./LICENSE).

leetcode/easy/175. Combine Two Tables.sql

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+/*
+Question 175. Combine Two Tables
+Link: https://leetcode.com/problems/combine-two-tables/description/
+
+Table: Person
+
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| personId    | int     |
+| lastName    | varchar |
+| firstName   | varchar |
++-------------+---------+
+personId is the primary key (column with unique values) for this table.
+This table contains information about the ID of some persons 
+and their first and last names.
+ 
+
+Table: Address
+
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| addressId   | int     |
+| personId    | int     |
+| city        | varchar |
+| state       | varchar |
++-------------+---------+
+addressId is the primary key (column with unique values) 
+for this table.
+Each row of this table contains information about the city 
+and state of one person with ID = PersonId.
+ 
+
+Write a solution to report the first name, last name, city, 
+and state of each person in the Person table. 
+If the address of a personId is not present in the Address table, 
+report null instead.
+
+Return the result table in any order.
+*/
+
+SELECT
+    Person.firstName,
+    Person.lastName,
+    Address.city,
+    Address.state
+FROM 
+    Person
+LEFT JOIN 
+    Address
+    ON 
+        Person.personId = Address.personId

leetcode/easy/182. Duplicate Emails.sql

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+/*
+Question 182. Duplicate emails
+Link: https://leetcode.com/problems/duplicate-emails/description/
+
+Table: Person
+
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| id          | int     |
+| email       | varchar |
++-------------+---------+
+id is the primary key (column with unique values) for this table.
+Each row of this table contains an email. 
+The emails will not contain uppercase letters.
+ 
+
+Write a solution to report all the duplicate emails. 
+Note that it's guaranteed that the email field is not NULL.
+
+Return the result table in any order.
+*/
+
+SELECT email 
+FROM Person
+GROUP BY email
+HAVING COUNT(id) > 1;

leetcode/easy/183. Customers Who Never Order.sql

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+/*
+Question 183. Customers Who Never Order.
+Link: https://leetcode.com/problems/customers-who-never-order/description/
+
+Table: Customers
+
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| id          | int     |
+| name        | varchar |
++-------------+---------+
+id is the primary key (column with unique values) for this table.
+Each row of this table indicates the ID and name of a customer.
+ 
+
+Table: Orders
+
++-------------+------+
+| Column Name | Type |
++-------------+------+
+| id          | int  |
+| customerId  | int  |
++-------------+------+
+id is the primary key (column with unique values) for this table.
+customerId is a foreign key (reference columns) 
+of the ID from the Customers table.
+Each row of this table indicates the ID 
+of an order and the ID of the customer who ordered it.
+ 
+
+Write a solution to find all customers who never order anything.
+
+Return the result table in any order.
+*/
+
+SELECT Customers.name AS Customers
+FROM Customers
+LEFT JOIN
+    Orders
+    ON
+        Customers.id = Orders.customerId
+WHERE Orders.id IS NULL

leetcode/easy/511. Game Play Analysis 1.sql

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+/*
+Question 511. Game Play Analysis 1.
+Link : https://leetcode.com/problems/game-play-analysis-i/description/
+
+Table: Activity
+
++--------------+---------+
+| Column Name  | Type    |
++--------------+---------+
+| player_id    | int     |
+| device_id    | int     |
+| event_date   | date    |
+| games_played | int     |
++--------------+---------+
+(player_id, event_date) is the primary key 
+(combination of columns with unique values) of this table.
+This table shows the activity of players of some games.
+Each row is a record of a player who logged in and played 
+a number of games (possibly 0) before logging out on someday using some device.
+ 
+
+Write a solution to find the first login date for each player.
+
+Return the result table in any order.
+*/
+
+SELECT 
+    player_id, 
+    MIN(event_date) AS first_login
+FROM Activity
+GROUP BY player_id