One-to-many embedding pattern in MongoDB - Mini Project: Build & Apply

One-to-many embedding pattern in MongoDB

📖 Scenario: You are building a simple database for a library. Each book can have multiple reviews from readers. You want to store each book's information along with its reviews inside a single document to keep related data together.

🎯 Goal: Create a MongoDB collection where each book document contains an embedded array of review documents. This shows how to use the one-to-many embedding pattern in MongoDB.

📋 What You'll Learn

Create a collection named books with one book document.

The book document must have fields title and author with exact values.

Add an embedded array field reviews inside the book document.

Each review in reviews must have reviewer and comment fields.

Insert exactly two reviews with specified values.

💡 Why This Matters

🌍 Real World

Embedding related data like reviews inside a book document keeps all information together, making it faster to read and simpler to manage in many applications.

💼 Career

Understanding one-to-many embedding in MongoDB is essential for designing efficient NoSQL databases used in web development, content management, and many data-driven applications.

1

Create the books collection with one book document

Create a MongoDB document for the books collection with the fields title set to 'The Great Gatsby' and author set to 'F. Scott Fitzgerald'. Insert this document into the books collection.

MongoDB

// Insert the book document into the books collection
// Your code here

Need a hint?

Use db.books.insertOne() with an object containing title and author.

2

Add an empty reviews array field to the book document

Update the existing book document in the books collection by adding an empty array field called reviews. Use updateOne with a filter on title and the $set operator.

MongoDB

db.books.insertOne({ title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' })
// Add an empty reviews array to the book document
// Your code here

Need a hint?

Use db.books.updateOne() with a filter on title and $set to add reviews: [].

3

Add two review documents inside the reviews array

Use updateOne with the $push operator and $each to add two review documents to the reviews array of the book with title 'The Great Gatsby'. The first review has reviewer 'Alice' and comment 'Loved the symbolism'. The second review has reviewer 'Bob' and comment 'A timeless classic'.

MongoDB

db.books.insertOne({ title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' })
db.books.updateOne({ title: 'The Great Gatsby' }, { $set: { reviews: [] } })
// Add two reviews to the reviews array
// Your code here

Need a hint?

Use $push with $each to add multiple review objects inside the reviews array.

4

Verify the final embedded document structure

Write a query using findOne to retrieve the book document with title 'The Great Gatsby' from the books collection. This will show the embedded reviews array inside the document.

MongoDB

db.books.insertOne({ title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' })
db.books.updateOne({ title: 'The Great Gatsby' }, { $set: { reviews: [] } })
db.books.updateOne(
  { title: 'The Great Gatsby' },
  { $push: { reviews: { $each: [
    { reviewer: 'Alice', comment: 'Loved the symbolism' },
    { reviewer: 'Bob', comment: 'A timeless classic' }
  ] } } }
)
// Retrieve the book document with embedded reviews
// Your code here

Need a hint?

Use db.books.findOne() with a filter on title to see the full document including embedded reviews.