$in for matching a set in MongoDB - Mini Project: Build & Apply

$in Operator for Matching a Set in MongoDB

📖 Scenario: You are managing a small online bookstore database. You want to find books that belong to certain genres from a list of genres.

🎯 Goal: Build a MongoDB query using the $in operator to find all books whose genre matches any genre in a given set.

📋 What You'll Learn

Create a collection called books with specific book documents

Define a list of genres to search for

Write a MongoDB query using $in to find books matching those genres

Complete the query to return only the matching books

💡 Why This Matters

🌍 Real World

Using $in helps quickly find records matching any value from a list, common in filtering products, users, or categories.

💼 Career

Database developers and data analysts often use $in to write efficient queries for filtering data sets.

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 search for

Create a variable called searchGenres and assign it the array ["Classic", "Science Fiction"].

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 the searchGenres array with the specified genres
// Your code here

Need a hint?

Use const searchGenres = ["Classic", "Science Fiction"] to define the array.

3

Write the MongoDB query using $in

Write a MongoDB query called query that uses { genre: { $in: searchGenres } } to find books whose genre is in the searchGenres 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 searchGenres = ["Classic", "Science Fiction"]

// Create the query object using $in with searchGenres
// Your code here

Need a hint?

Use const query = { genre: { $in: searchGenres } } to create the query.

4

Complete the query to find matching books

Use db.books.find(query) to find all books matching the genres in searchGenres.

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 searchGenres = ["Classic", "Science Fiction"]

const query = { genre: { $in: searchGenres } }

// Use db.books.find(query) to get matching books
// Your code here

Need a hint?

Use db.books.find(query) to retrieve the matching documents.