Auto-generated _id behavior in MongoDB - Mini Project: Build & Apply

Understanding Auto-generated _id Behavior in MongoDB

📖 Scenario: You are managing a small online bookstore database using MongoDB. Each book entry needs a unique identifier to keep track of it easily.

🎯 Goal: Learn how MongoDB automatically creates a unique _id for each document when you insert data without specifying an _id.

📋 What You'll Learn

Create a collection named books with no documents initially.

Insert a document without specifying the _id field.

Insert another document explicitly specifying the _id field.

Query the collection to see the documents and their _id values.

💡 Why This Matters

🌍 Real World

Unique identifiers like <code>_id</code> are essential in databases to track and manage records without confusion.

💼 Career

Understanding how MongoDB generates and uses <code>_id</code> fields is important for database administrators and developers working with NoSQL databases.

1

Create the books collection

Create an empty collection called books in your MongoDB database.

MongoDB

// Create the books collection
// Your code here

Need a hint?

Use db.createCollection('books') to create the collection.

2

Insert a document without specifying _id

Insert a document into the books collection with these exact fields: { title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' }. Do not include the _id field.

MongoDB

db.createCollection('books')
// Insert the first book document without _id
// Your code here

Need a hint?

Use db.books.insertOne() with the specified fields, but no _id.

3

Insert a document with an explicit _id

Insert another document into the books collection with these exact fields: { _id: 1001, title: '1984', author: 'George Orwell' }. This time include the _id field explicitly set to 1001.

MongoDB

db.createCollection('books')
db.books.insertOne({ title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' })
// Insert the second book document with _id 1001
// Your code here

Need a hint?

Use db.books.insertOne() with the _id field set to 1001.

4

Query the books collection to see all documents

Write a query to find all documents in the books collection and return them.

MongoDB

db.createCollection('books')
db.books.insertOne({ title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' })
db.books.insertOne({ _id: 1001, title: '1984', author: 'George Orwell' })
// Query all documents in books
// Your code here

Need a hint?

Use db.books.find() to retrieve all documents.