task: #3570 & All fremium easy completed

Ivanbyone · Ivanbyone · commit 9afb08aa1fa9 · 2025-07-19T19:00:36.000+03:00
diff --git a/README.md b/README.md
@@ -159,6 +159,7 @@ Useful for preparing for technical interviews and improving your SQL skills.
     - [2356. Number of Unique Subjects Taught by Each Teacher](./leetcode/easy/2356.%20Number%20of%20Unique%20Subjects%20Taught%20by%20Each%20Teacher.sql)
     - [3436. Find Valid Emails](./leetcode/easy/3436.%20Find%20Valid%20Emails.sql)
     - [3465. Find Products with Valid Serial Numbers](./leetcode/easy/3465.%20Find%20Products%20with%20Valid%20Serial%20Numbers.sql)
+    - [3570. Find Books with No Available Copies](./leetcode/easy/3570.%20Find%20Books%20with%20No%20Available%20Copies.sql)
 2. [Medium](./leetcode/medium/)
     - [176. Second Highest Salary](./leetcode/medium/176.%20Second%20Highest%20Salary.sql)
     - [180. Consecutive Numbers](./leetcode/medium/180.%20Consecutive%20Numbers.sql)
diff --git a/leetcode/easy/3570. Find Books with No Available Copies.sql b/leetcode/easy/3570. Find Books with No Available Copies.sql
@@ -0,0 +1,59 @@
+/*
+Question 3570. Find Books with No Available Copies
+Link: https://leetcode.com/problems/find-books-with-no-available-copies/description/?envType=problem-list-v2&envId=database
+
+Table: library_books
+
++------------------+---------+
+| Column Name      | Type    |
++------------------+---------+
+| book_id          | int     |
+| title            | varchar |
+| author           | varchar |
+| genre            | varchar |
+| publication_year | int     |
+| total_copies     | int     |
++------------------+---------+
+book_id is the unique identifier for this table.
+Each row contains information about a book in the library, including the total number of copies owned by the library.
+Table: borrowing_records
+
++---------------+---------+
+| Column Name   | Type    |
++---------------+---------+
+| record_id     | int     |
+| book_id       | int     |
+| borrower_name | varchar |
+| borrow_date   | date    |
+| return_date   | date    |
++---------------+---------+
+record_id is the unique identifier for this table.
+Each row represents a borrowing transaction and return_date is NULL if the book is currently borrowed and hasn't been returned yet.
+Write a solution to find all books that are currently borrowed (not returned) and have zero copies available in the library.
+
+A book is considered currently borrowed if there exists a borrowing record with a NULL return_date
+Return the result table ordered by current borrowers in descending order, then by book title in ascending order.
+*/
+
+WITH br AS (
+    SELECT 
+        book_id,
+        COUNT(book_id) AS current_borrowers
+    FROM borrowing_records
+    WHERE return_date IS NULL
+    GROUP BY book_id
+)
+
+SELECT
+    lb.book_id,
+    lb.title,
+    lb.author,
+    lb.genre,
+    lb.publication_year,
+    br.current_borrowers
+FROM library_books AS lb
+INNER JOIN
+    br
+    ON lb.book_id = br.book_id
+WHERE (lb.total_copies - br.current_borrowers) = 0
+ORDER BY br.current_borrowers DESC, lb.title ASC
