📘 MongoDB & Express.js — A Complete Guide

🔍 What is MongoDB?

MongoDB is a NoSQL database that stores data in the form of documents (similar to JSON objects).
It uses a JavaScript-like syntax and is ideal for handling large volumes of unstructured or semi-structured data.

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🖥️ MongoDB Compass

A GUI tool to visually manage your MongoDB databases and collections.
Use it to:

• Create databases and collections
• Insert, view, update, delete documents
• Run queries without using the shell

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📂 Key Concepts

Term	Description
Database	Logical container for collections. Example: Sigma
Collection	Like a table in SQL. Contains multiple documents. Example: Courses
Document	A single record in JSON-like format inside a collection.
MongoDB Shell	CLI tool to interact with MongoDB directly using commands.

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🧪 Basic MongoDB Shell Commands

// List all databases
show databases;

// Switch to or create a database
use CrudDb;

// List all collections in current database
show collections;

// View all documents inside 'courses' collection
db.courses.find();

// Insert a single document into 'courses'
db.courses.insertOne({ name: "JavaScript" });

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🛠️ Project Setup: MongoDB with Express.js + Mongoose

📁 Files

• Mongoose-With-Express.js → Main server file using Express
• models/ToDo.js → Mongoose schema/model for ToDo items

🚀 Running the Project

npm install
node Mongoose-With-Express.js

Make sure MongoDB is running locally on default port 27017.

📄 Example Endpoints

➕ Create a ToDo

GET / Creates a new ToDo document with random days and default values.

📄 Read a ToDo

GET /a Fetches one ToDo document and returns its title and desc. Returns a 404 if no document is found.

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📦 What is Mongoose?

Mongoose is an advanced MongoDB object modeling tool for Node.js.

🛠 Why Use Mongoose?

• Schema-based structure and validation
• Model-based interactions
• Middleware and hooks
• Built-in query builders

📌 Key Benefits

Feature	Mongoose	MongoDB Native Driver
Schema Support	✅ Yes	❌ No
Middleware	✅ Yes	❌ No
Easy Relationships	✅ Populate, References	❌ Manual
Validation	✅ Built-in	❌ Manual

📦 Install Mongoose

npm install mongoose

🔄 CRUD Operations Summary

Operation	Mongoose Method	Description
Create	save(), create()	Add new document to a collection
Read	find(), findOne()	Retrieve document(s) from collection
Update	updateOne(), findByIdAndUpdate()	Modify existing document(s)
Delete	deleteOne(), findByIdAndDelete()	Remove document(s)

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📚 Useful MongoDB Operators

Operator	Use Case
$set	Update a field’s value
$gt, $lt	Greater than, Less than filtering
$and, $or	Combine multiple query conditions
$in, $nin	Match values in / not in an array

🧠 Learn more :- MongoDB Query Operators

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🙌 Credits

Tutorial followed from CodeWithHarry — Haris Ali Khan 📺 Sigma Web Development Course - MongoDB + Mongoose

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🔗 Resources

• 🧾 Official MongoDB Manual
• 📘 Mongoose Docs
• 🛠️ MongoDB Playground on MongoDB Atlas
• 🖥️ MongoDB Compass Download