Why result control matters in MongoDB - See It in Action

Why Result Control Matters in MongoDB Queries

📖 Scenario: You are managing a small online bookstore database using MongoDB. You want to find books by a specific author but only want to see the book titles and their prices, not all the details. This helps you focus on the important information quickly.

🎯 Goal: Build a MongoDB query that finds books by the author "Jane Austen" and returns only the title and price fields. This shows how controlling the result fields helps get just the data you need.

📋 What You'll Learn

Create a collection named books with sample book documents.

Add a variable to specify the author name to search for.

Write a MongoDB query to find books by that author.

Use projection to return only the title and price fields.

💡 Why This Matters

🌍 Real World

In real-world applications, controlling query results helps reduce data transfer and focus on relevant information, improving performance and user experience.

💼 Career

Database developers and analysts often need to write efficient queries that return only necessary fields to optimize applications and reports.

1

DATA SETUP: Create the books collection with sample data

Create a variable called books that holds an array of three book documents. Each document must have these exact fields and values: { title: "Pride and Prejudice", author: "Jane Austen", price: 9.99, year: 1813 }, { title: "Emma", author: "Jane Austen", price: 12.99, year: 1815 }, and { title: "Moby Dick", author: "Herman Melville", price: 15.50, year: 1851 }.

MongoDB

# Create the books array with the three exact documents
# Your code here

Need a hint?

Use a list of dictionaries with the exact keys and values given.

2

CONFIGURATION: Define the author to search for

Create a variable called search_author and set it to the string "Jane Austen".

MongoDB

books = [
    { "title": "Pride and Prejudice", "author": "Jane Austen", "price": 9.99, "year": 1813 },
    { "title": "Emma", "author": "Jane Austen", "price": 12.99, "year": 1815 },
    { "title": "Moby Dick", "author": "Herman Melville", "price": 15.50, "year": 1851 }
]
# Define the author to search for
# Your code here

Need a hint?

Just assign the exact string to the variable search_author.

3

CORE LOGIC: Write a MongoDB query to find books by the author

Create a variable called query that holds the MongoDB query object to find documents where the author field equals the value in search_author.

MongoDB

books = [
    { "title": "Pride and Prejudice", "author": "Jane Austen", "price": 9.99, "year": 1813 },
    { "title": "Emma", "author": "Jane Austen", "price": 12.99, "year": 1815 },
    { "title": "Moby Dick", "author": "Herman Melville", "price": 15.50, "year": 1851 }
]
search_author = "Jane Austen"
# Create the query object to find books by search_author
# Your code here

Need a hint?

The query object matches documents where the author field equals the search_author variable.

4

COMPLETION: Use projection to return only title and price

Create a variable called projection that includes only the title and price fields with value 1 to include them in the results, and excludes the _id field by setting it to 0.

MongoDB

books = [
    { "title": "Pride and Prejudice", "author": "Jane Austen", "price": 9.99, "year": 1813 },
    { "title": "Emma", "author": "Jane Austen", "price": 12.99, "year": 1815 },
    { "title": "Moby Dick", "author": "Herman Melville", "price": 15.50, "year": 1851 }
]
search_author = "Jane Austen"
query = { "author": search_author }
# Create the projection object to include only title and price, exclude _id
# Your code here

Need a hint?

Use 1 to include fields and 0 to exclude the _id field.