Add lesson for cleaning up data

src/data/courses/sql/chapters/manipulating-data/lessons/cleaning-up-data.md

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+---
+title: Deleting Books
+description: Practice removing data from a bookstore inventory
+order: 135
+type: challenge
+setup: |
+  ```sql
+  CREATE TABLE books (
+      id INTEGER PRIMARY KEY,
+      title VARCHAR(100),
+      author VARCHAR(100),
+      price DECIMAL(10,2),
+      stock INTEGER,
+      category VARCHAR(50)
+  );
+
+  INSERT INTO books (id, title, author, price, stock, category) VALUES
+      (1, 'The Great Gatsby', 'F. Scott Fitzgerald', 15.99, 0, 'Fiction'),
+      (2, 'SQL Basics', 'Jane Smith', 29.99, 5, 'Technical'),
+      (3, '1984', 'George Orwell', 12.99, 0, 'Fiction'),
+      (4, 'Poetry Collection', 'Various Authors', 19.99, 2, 'Poetry'),
+      (5, 'Database Design', 'John Doe', 34.99, 0, 'Technical');
+  ```
+---
+
+Given the following `books` table:
+
+| id  | title             | author              | price | stock | category  |
+| --- | ----------------- | ------------------- | ----- | ----- | --------- |
+| 1   | The Great Gatsby  | F. Scott Fitzgerald | 15.99 | 0     | Fiction   |
+| 2   | SQL Basics        | Jane Smith          | 29.99 | 5     | Technical |
+| 3   | 1984              | George Orwell       | 12.99 | 0     | Fiction   |
+| 4   | Poetry Collection | Various Authors     | 19.99 | 2     | Poetry    |
+| 5   | Database Design   | John Doe            | 34.99 | 0     | Technical |
+
+The bookstore manager wants to clean up the inventory database. Write `DELETE` statements to:
+
+1. Remove all books that are out of stock (`stock = 0`)
+2. Delete any Technical books that cost more than $30
+3. Remove the book with `id = 4`
+
+## Expected Results
+
+After your DELETE operations, the table should look like this:
+
+| id  | title      | author     | price | stock | category  |
+| --- | ---------- | ---------- | ----- | ----- | --------- |
+| 2   | SQL Basics | Jane Smith | 29.99 | 5     | Technical |
+
+> Remember to use semicolons to separate multiple DELETE statements.