updateMany method in MongoDB - Mini Project: Build & Apply

Using the updateMany Method in MongoDB

📖 Scenario: You manage a small online bookstore database. You want to update the prices of all books in a specific category to offer a discount.

🎯 Goal: Learn how to use the updateMany method in MongoDB to update multiple documents at once based on a condition.

📋 What You'll Learn

Create a collection named books with sample book documents.

Define a filter to select books in the 'Science Fiction' category.

Use updateMany to reduce the price of all selected books by 10%.

Verify the update operation is correctly structured.

💡 Why This Matters

🌍 Real World

Updating prices or statuses of multiple products or records in a database at once is common in e-commerce and inventory management.

💼 Career

Knowing how to use updateMany helps database administrators and backend developers efficiently manage bulk updates in MongoDB.

1

Create the books collection with sample documents

Create a variable called books and assign it an array of three book documents with these exact fields and values: { title: 'Dune', category: 'Science Fiction', price: 20 }, { title: '1984', category: 'Science Fiction', price: 15 }, and { title: 'Pride and Prejudice', category: 'Romance', price: 10 }.

MongoDB

const books = [
  // Your code here
];

Need a hint?

Remember to create an array with three objects exactly as described.

2

Define the filter for books in the 'Science Fiction' category

Create a variable called filter and set it to an object that selects documents where the category field is exactly 'Science Fiction'.

MongoDB

const books = [
  { title: 'Dune', category: 'Science Fiction', price: 20 },
  { title: '1984', category: 'Science Fiction', price: 15 },
  { title: 'Pride and Prejudice', category: 'Romance', price: 10 }
];

const filter = {
  // Your code here
};

Need a hint?

Use an object with the key category and value 'Science Fiction'.

3

Write the update operation to reduce prices by 10%

Create a variable called update and set it to an object that uses the $mul operator to multiply the price field by 0.9 (to reduce price by 10%).

MongoDB

const books = [
  { title: 'Dune', category: 'Science Fiction', price: 20 },
  { title: '1984', category: 'Science Fiction', price: 15 },
  { title: 'Pride and Prejudice', category: 'Romance', price: 10 }
];

const filter = { category: 'Science Fiction' };

const update = {
  // Your code here
};

Need a hint?

Use the $mul operator inside the update object to multiply the price.

4

Use updateMany to apply the price reduction

Write a line calling db.books.updateMany(filter, update); to update all books matching the filter with the price reduction.

MongoDB

const books = [
  { title: 'Dune', category: 'Science Fiction', price: 20 },
  { title: '1984', category: 'Science Fiction', price: 15 },
  { title: 'Pride and Prejudice', category: 'Romance', price: 10 }
];

const filter = { category: 'Science Fiction' };

const update = { $mul: { price: 0.9 } };

// Your code here

Need a hint?

Use the updateMany method on db.books with the filter and update variables.