Document Database

Definition: A document database is a type of NoSQL database that stores data as flexible documents, usually in a JSON-like format, instead of fixed rows and columns.
Each document can have a different structure, which makes it useful when your data changes or contains nested information.

Simple example

Instead of this relational structure:

Users
----------------
id | name | email
1  | Ali  | ali@mail.com
 
Orders
----------------
id | user_id | product
10 | 1       | Laptop

A document database could store the user and their related information together:

{
  "id": 1,
  "name": "Ali",
  "email": "ali@mail.com",
  "orders": [
    {
      "product": "Laptop",
      "price": 1200
    }
  ]
}

So the idea is basically:

Relational DB → tables → rows → columns → relationships

Document DB → collections → documents → fields/values (MongoDB University)

3 examples

1. E-commerce: Store a product with its specifications, images, reviews, and different variants inside a flexible document.

2. Social media: Store a user’s profile together with preferences, interests, and settings that may differ from user to user.

3. IoT: Store sensor readings where different devices may produce different types of data. (MongoDB)

Common example

MongoDB is a popular document database. It stores documents in a JSON-like format called BSON. (Google Cloud)

Easy way to remember:

Relational database = spreadsheet-like tables.
Document database = JSON-like objects.

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