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

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

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

Adding a New Movie:

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

Finding a User's Favorite Movies:

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

Updating a Movie's Information:

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

Deleting a Movie Released Before a Certain Year:

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

Try it yourself

Create User Documents: Add three user documents with different favorite movies.
Query Movies: Find all movies with the genre “Sci-Fi.”
Update User Email: Update a user’s email address.
Delete a Movie: Delete a movie by title from the movies collection.

Introduction to MongoDB for Web Development