$nin for not in set in MongoDB - Mini Project: Build & Apply

$nin for not in set in MongoDB

📖 Scenario: You are managing a small online bookstore database. You want to find books that are not in certain genres to recommend to customers who want something different.

🎯 Goal: Build a MongoDB query using the $nin operator to find books whose genre is not in a given list of genres.

📋 What You'll Learn

Create a collection called books with specific book documents

Define a list of genres to exclude

Write a query using $nin to find books not in those genres

Complete the query to return only the book titles

💡 Why This Matters

🌍 Real World

Filtering data to exclude certain categories is common in recommendation systems, reporting, and data analysis.

💼 Career

Understanding $nin helps in writing flexible MongoDB queries for real-world applications like filtering products, users, or content.

1

Create the books collection with sample data

Create a MongoDB collection called books and insert these exact documents: { title: "The Hobbit", genre: "Fantasy" }, { title: "1984", genre: "Dystopian" }, { title: "To Kill a Mockingbird", genre: "Classic" }, { title: "The Great Gatsby", genre: "Classic" }, { title: "Neuromancer", genre: "Science Fiction" }.

MongoDB

// Insert the specified book documents into the books collection
// Your code here

Need a hint?

Use db.books.insertMany([...]) with the exact documents listed.

2

Define the list of genres to exclude

Create a variable called excludedGenres and set it to an array containing the strings "Classic" and "Dystopian".

MongoDB

db.books.insertMany([
  { title: "The Hobbit", genre: "Fantasy" },
  { title: "1984", genre: "Dystopian" },
  { title: "To Kill a Mockingbird", genre: "Classic" },
  { title: "The Great Gatsby", genre: "Classic" },
  { title: "Neuromancer", genre: "Science Fiction" }
])

// Define excludedGenres array with "Classic" and "Dystopian"
// Your code here

Need a hint?

Use const excludedGenres = ["Classic", "Dystopian"] to define the array.

3

Write the query using $nin to find books not in excluded genres

Write a MongoDB query called query that finds documents in books where the genre field is $nin the excludedGenres array.

MongoDB

db.books.insertMany([
  { title: "The Hobbit", genre: "Fantasy" },
  { title: "1984", genre: "Dystopian" },
  { title: "To Kill a Mockingbird", genre: "Classic" },
  { title: "The Great Gatsby", genre: "Classic" },
  { title: "Neuromancer", genre: "Science Fiction" }
])

const excludedGenres = ["Classic", "Dystopian"]

// Create a query object using $nin with excludedGenres
// Your code here

Need a hint?

Use { genre: { $nin: excludedGenres } } to build the query object.

4

Complete the query to return only book titles

Write a MongoDB find command using query to find matching books in books and project only the title field (exclude _id). Save this to a variable called result.

MongoDB

db.books.insertMany([
  { title: "The Hobbit", genre: "Fantasy" },
  { title: "1984", genre: "Dystopian" },
  { title: "To Kill a Mockingbird", genre: "Classic" },
  { title: "The Great Gatsby", genre: "Classic" },
  { title: "Neuromancer", genre: "Science Fiction" }
])

const excludedGenres = ["Classic", "Dystopian"]

const query = { genre: { $nin: excludedGenres } }

// Use find with query and project only title (exclude _id), assign to result
// Your code here

Need a hint?

Use db.books.find(query, { title: 1, _id: 0 }) to get only titles.