Normalization vs denormalization default in MongoDB - Hands-On Comparison

Understanding Normalization vs Denormalization in MongoDB

📖 Scenario: You are working on a simple online bookstore database using MongoDB. You want to understand how to organize your data using normalization and denormalization techniques.

🎯 Goal: Build two collections: one using normalization (separate collections with references) and one using denormalization (embedding related data). Learn how to create these structures step-by-step.

📋 What You'll Learn

Create a books collection with book details

Create an authors collection with author details

Create a normalized structure by referencing authors in books

Create a denormalized structure by embedding author details inside books

💡 Why This Matters

🌍 Real World

Many real-world applications use MongoDB to store data. Understanding when to normalize or denormalize data helps design efficient and easy-to-use databases.

💼 Career

Database developers and backend engineers often decide how to structure data for performance and maintainability. Knowing normalization and denormalization is essential for these roles.

1

Create the authors collection

Create a collection called authors with these exact documents: { _id: 1, name: "Jane Austen" } and { _id: 2, name: "Mark Twain" }.

MongoDB

// Your code here to create authors collection with two documents

Need a hint?

Use insertMany to add multiple documents to the authors collection.

2

Create the books collection with author references (Normalization)

Create a collection called books with these exact documents: { title: "Pride and Prejudice", author_id: 1 } and { title: "Adventures of Huckleberry Finn", author_id: 2 }. Use author_id to reference authors.

MongoDB

db.authors.insertMany([
  { _id: 1, name: "Jane Austen" },
  { _id: 2, name: "Mark Twain" }
])
// Your code here to create books collection with author references

Need a hint?

Use author_id to link books to authors by their _id.

3

Create the books_denormalized collection with embedded author details (Denormalization)

Create a collection called books_denormalized with these exact documents: { title: "Pride and Prejudice", author: { name: "Jane Austen" } } and { title: "Adventures of Huckleberry Finn", author: { name: "Mark Twain" } }. Embed author details inside each book document.

MongoDB

db.authors.insertMany([
  { _id: 1, name: "Jane Austen" },
  { _id: 2, name: "Mark Twain" }
])
db.books.insertMany([
  { title: "Pride and Prejudice", author_id: 1 },
  { title: "Adventures of Huckleberry Finn", author_id: 2 }
])
// Your code here to create books_denormalized collection with embedded author details

Need a hint?

Embed the author object inside each book document instead of using a reference.

4

Add an index on author_id in books collection

Create an index on the author_id field in the books collection to speed up queries that find books by author.

MongoDB

db.authors.insertMany([
  { _id: 1, name: "Jane Austen" },
  { _id: 2, name: "Mark Twain" }
])
db.books.insertMany([
  { title: "Pride and Prejudice", author_id: 1 },
  { title: "Adventures of Huckleberry Finn", author_id: 2 }
])
db.books_denormalized.insertMany([
  { title: "Pride and Prejudice", author: { name: "Jane Austen" } },
  { title: "Adventures of Huckleberry Finn", author: { name: "Mark Twain" } }
])
// Your code here to create an index on author_id in books collection

Need a hint?

Use createIndex on the author_id field in the books collection.