Add price range analysis challenge

src/data/courses/sql-mastery/chapters/window-functions/lessons/price-range-analysis.md

@@ -0,0 +1,88 @@
+---
+title: Price Range Analysis
+description: Practice using RANGE in window frames to analyze similar-priced books
+order: 180
+type: challenge
+setup: |
+  ```sql
+  CREATE TABLE book (
+      id INT PRIMARY KEY,
+      title VARCHAR(100),
+      category VARCHAR(50),
+      price DECIMAL(10,2),
+      copies_sold INT
+  );
+
+  INSERT INTO book (id, title, category, price, copies_sold) VALUES
+      (1, 'SQL Basics', 'Programming', 29.99, 1500),
+      (2, 'Advanced SQL', 'Programming', 49.99, 2500),
+      (3, 'Data Science', 'Data Analysis', 39.99, 2000),
+      (4, 'Web Development', 'Programming', 34.99, 1800),
+      (5, 'Statistics 101', 'Data Analysis', 24.99, 1200),
+      (6, 'Python Basics', 'Programming', 29.99, 3000),
+      (7, 'Machine Learning', 'Data Analysis', 44.99, 2200),
+      (8, 'Database Design', 'Programming', 34.99, 1700),
+      (9, 'R Programming', 'Data Analysis', 34.99, 1600);
+  ```
+---
+
+The bookstore wants to analyze how books perform compared to other books with similar prices. For each book, they want to see the average sales of books within $5 of its price (i.e. if the book is priced at 20, they want to see the average sales of books priced between 15 and 25).
+
+Given the following data in table `book`:
+
+| id  | title            | category      | price | copies_sold |
+| --- | ---------------- | ------------- | ----- | ----------- |
+| 1   | SQL Basics       | Programming   | 29.99 | 1500        |
+| 2   | Advanced SQL     | Programming   | 49.99 | 2500        |
+| 3   | Data Science     | Data Analysis | 39.99 | 2000        |
+| 4   | Web Development  | Programming   | 34.99 | 1800        |
+| 5   | Statistics 101   | Data Analysis | 24.99 | 1200        |
+| 6   | Python Basics    | Programming   | 29.99 | 3000        |
+| 7   | Machine Learning | Data Analysis | 44.99 | 2200        |
+| 8   | Database Design  | Programming   | 34.99 | 1700        |
+| 9   | R Programming    | Data Analysis | 34.99 | 1600        |
+
+Write a query that shows:
+
+- Book title
+- Price
+- Book's copies sold
+- Average copies sold of similarly priced books (within $5 range)
+- Number of books in that price range
+
+Order the results by price (ascending) and title (ascending).
+
+## Expected Output
+
+| title            | price | copies_sold | similar_price_avg | books_in_range |
+| ---------------- | ----- | ----------- | ----------------- | -------------- |
+| Statistics 101   | 24.99 | 1200        | 1900              | 3              |
+| Python Basics    | 29.99 | 3000        | 1800              | 6              |
+| SQL Basics       | 29.99 | 1500        | 1800              | 6              |
+| Database Design  | 34.99 | 1700        | 1933              | 6              |
+| R Programming    | 34.99 | 1600        | 1933              | 6              |
+| Web Development  | 34.99 | 1800        | 1933              | 6              |
+| Data Science     | 39.99 | 2000        | 1860              | 5              |
+| Machine Learning | 44.99 | 2200        | 2233              | 3              |
+| Advanced SQL     | 49.99 | 2500        | 2350              | 2              |
+
+> **Note:** You can use the `RANGE BETWEEN 5 PRECEDING AND 5 FOLLOWING` clause to create a window that includes all rows where the price is within ±$5 of the current row's price.
+
+## Solution
+
+```sql
+SELECT
+    title,
+    price,
+    copies_sold,
+    ROUND(AVG(copies_sold) OVER (
+        ORDER BY price
+        RANGE BETWEEN 5 PRECEDING AND 5 FOLLOWING
+    )) as similar_price_avg,
+    COUNT(*) OVER (
+        ORDER BY price
+        RANGE BETWEEN 5 PRECEDING AND 5 FOLLOWING
+    ) as books_in_range
+FROM book
+ORDER BY price, title;
+```