deleteMany method in MongoDB - Mini Project: Build & Apply

Using the deleteMany Method in MongoDB

📖 Scenario: You manage a small online bookstore database. Over time, some books become outdated or irrelevant. You want to clean up your database by removing all books from a specific author.

🎯 Goal: Learn how to use the deleteMany method in MongoDB to remove multiple documents that match a condition.

📋 What You'll Learn

Create a collection called books with specific book entries

Define a filter to select books by a certain author

Use the deleteMany method with the filter to remove those books

Verify the final state of the books collection after deletion

💡 Why This Matters

🌍 Real World

Cleaning up outdated or irrelevant data in a database is common in real-world applications to keep data accurate and storage efficient.

💼 Career

Database administrators and backend developers often use deleteMany to manage large datasets by removing multiple records at once based on conditions.

1

Create the books collection with sample data

Create a variable called books that is an array of documents. Include these exact entries: { title: "Learn MongoDB", author: "John Doe", year: 2018 }, { title: "Advanced MongoDB", author: "Jane Smith", year: 2020 }, { title: "MongoDB Basics", author: "John Doe", year: 2017 }, { title: "Node.js Guide", author: "Alice Brown", year: 2019 }.

MongoDB

// Create the books array with the specified documents
// Your code here

Need a hint?

Use const books = [ ... ] and include all four book objects exactly as shown.

2

Define a filter to select books by author "John Doe"

Create a variable called filter and set it to an object that matches documents where the author field is exactly "John Doe".

MongoDB

const books = [
  { title: "Learn MongoDB", author: "John Doe", year: 2018 },
  { title: "Advanced MongoDB", author: "Jane Smith", year: 2020 },
  { title: "MongoDB Basics", author: "John Doe", year: 2017 },
  { title: "Node.js Guide", author: "Alice Brown", year: 2019 }
];

// Define the filter to select books by John Doe
const filter = { author: "John Doe" };

Need a hint?

Use const filter = { author: "John Doe" }; to create the filter object.

3

Use deleteMany to remove books by "John Doe"

Assuming you have a MongoDB collection object called booksCollection, write a line that calls deleteMany on booksCollection using the filter variable to delete all books by "John Doe".

MongoDB

const books = [
  { title: "Learn MongoDB", author: "John Doe", year: 2018 },
  { title: "Advanced MongoDB", author: "Jane Smith", year: 2020 },
  { title: "MongoDB Basics", author: "John Doe", year: 2017 },
  { title: "Node.js Guide", author: "Alice Brown", year: 2019 }
];

const filter = { author: "John Doe" };

// Use deleteMany on booksCollection with filter
booksCollection.deleteMany(filter);

Need a hint?

Call booksCollection.deleteMany(filter); to delete matching documents.

4

Verify the remaining books after deletion

Write a line that calls find() on booksCollection without any filter to get all remaining books.

MongoDB

const books = [
  { title: "Learn MongoDB", author: "John Doe", year: 2018 },
  { title: "Advanced MongoDB", author: "Jane Smith", year: 2020 },
  { title: "MongoDB Basics", author: "John Doe", year: 2017 },
  { title: "Node.js Guide", author: "Alice Brown", year: 2019 }
];

const filter = { author: "John Doe" };

booksCollection.deleteMany(filter);

// Get all remaining books
booksCollection.find();

Need a hint?

Use booksCollection.find(); to retrieve all remaining documents.