Introduction to MongoDB for Web Development

Introduction

MongoDB is a NoSQL database system that stores data in a flexible, JSON-like format called BSON (Binary JSON). Unlike SQL databases, which store data in tables with rows and columns, MongoDB organizes data in documents that are grouped in collections. This schema-less structure makes MongoDB particularly useful for web applications where data structures may evolve over time. In this lesson, we’ll cover MongoDB basics and practice creating and managing a simple movie application database.

Key Concepts and Definitions

• Database: A container for collections in MongoDB. Each database holds multiple collections, similar to how a relational database holds tables.

• Collection: A group of MongoDB documents, somewhat analogous to a table in an SQL database. Collections store documents with potentially diverse structures.

• Document: The basic unit of data in MongoDB, stored as a BSON object. It typically represents a record with fields and values.

Example: For a movie app, we could have:

• A database named movieApp.

• Collections such as users and movies.

• Documents within these collections representing individual users or movies.

Step-by-Step Explanation

1. Setting Up MongoDB and Creating a Database

1. Connect to MongoDB: Open MongoDB Compass (GUI) or use the MongoDB shell/CLI.

2. Create a Database:

    use movieApp; // This creates a database named movieApp or switches to it if it already exists
   

2. Creating Collections in MongoDB

You can create a collection by simply inserting a document. MongoDB will create the collection automatically.

db.createCollection("users");
db.createCollection("movies");

3. Basic CRUD Operations on Documents

Create (Insert)

Adding documents to a collection in MongoDB:

• Insert One Document:

    db.users.insertOne({
        username: "john_doe",
        email: "john@example.com"
    });
  

• Insert Multiple Documents:

    db.movies.insertMany([
        { title: "Inception", genre: "Sci-Fi", year: 2010 },
        { title: "The Matrix", genre: "Action", year: 1999 }
    ]);
  

Read (Query)

Retrieving data from a collection:

• Find One Document:

    db.movies.findOne({ title: "Inception" });
  

• Find All Documents:

    db.movies.find({});
  

Update

Modifying documents in a collection:

• Update One Document:

    db.users.updateOne(
        { username: "john_doe" },
        { $set: { email: "john.new@example.com" } }
    );
  

• Update Multiple Documents:

    db.movies.updateMany(
        { genre: "Action" },
        { $set: { genre: "Action/Adventure" } }
    );
  

Delete

Removing documents from a collection:

• Delete One Document:

    db.users.deleteOne({ username: "john_doe" });
  

• Delete Multiple Documents:

    db.movies.deleteMany({ year: { $lt: 2000 } });
  

4. Building a Movie App Database

In a movie application, we’ll define two collections: users and movies. Each collection will hold relevant documents, and we’ll set up basic CRUD operations.

• Create users Collection and Add Documents:

    db.users.insertOne({
        username: "jane_doe",
        email: "jane@example.com",
        favoriteMovies: ["Inception", "The Matrix"]
    });
  

• Create movies Collection and Add Documents:

    db.movies.insertMany([
        { title: "Avatar", genre: "Sci-Fi", year: 2009 },
        { title: "Titanic", genre: "Drama", year: 1997 }
    ]);
  

Examples of CRUD Operations for the Movie App

1. Adding a New Movie:

    db.movies.insertOne({
        title: "Interstellar",
        genre: "Sci-Fi",
        year: 2014
    });
   

2. Finding a User's Favorite Movies:

    db.users.findOne({ username: "jane_doe" });
   

3. Updating a Movie's Information:

    db.movies.updateOne(
        { title: "Avatar" },
        { $set: { genre: "Science Fiction" } }
    );
   

4. Deleting a Movie Released Before a Certain Year:

    db.movies.deleteMany({ year: { $lt: 2000 } });
   

Try it yourself

1. Create User Documents: Add three user documents with different favorite movies.

2. Query Movies: Find all movies with the genre “Sci-Fi.”

3. Update User Email: Update a user’s email address.

4. Delete a Movie: Delete a movie by title from the movies collection.