Introduction

What is MongoDB?

MongoDB is a NoSQL (non-relational) database that stores data in a document-oriented format using JSON-like objects called BSON (Binary JSON). Unlike traditional relational databases that use tables and rows, MongoDB uses collections and documents.

Key Features

• Document-Oriented Storage – Data is stored in flexible, schema-less JSON-like documents.
• Scalability – Supports horizontal scaling using sharding.
• High Performance – Optimized for read and write operations.
• Indexing – Supports various types of indexes to improve query performance.
• Aggregation Framework – Used to process data and perform operations like filtering, grouping, and sorting.
• Replication – Provides high availability using replica sets.

Basic Terminology

• Database – A container for collections.
• Collection – A group of related documents (similar to a table in SQL).
• Document – A single record in MongoDB stored as a BSON object.
• Field – A key-value pair inside a document (similar to a column).
• _id – A unique identifier automatically generated for each document.

Example Document

{
  "_id": 1,
  "name": "Rajesh Singh",
  "age": 25,
  "skills": ["HTML", "CSS", "JavaScript", "Python", "Node.js"]
}

Comparison with SQL Databases

SQL Database	MongoDB
Table	Collection
Row	Document
Column	Field
Primary Key	_id
Joins	Embedded Documents / $lookup
Schema	Schema-less

Advantages

• Flexible data structure (no need to define schema in advance)
• Easy to scale horizontally
• High speed for large-scale applications
• JSON-like syntax makes it developer-friendly

Use Cases

• Real-time analytics
• Content management systems
• IoT and sensor data storage
• E-commerce platforms
• Social media applications

Installation & Basic Commands

• Start MongoDB Shell:

mongosh

• Show databases:

show dbs

• Use or create a database:

use myDatabase

• Show collections:

show collections

• Insert a document:

db.users.insertOne({ name: "Harry", age: 22 })

• Find documents:

db.users.find()