What are Document-Based NoSQL Systems?

Document-based NoSQL databases store data in the form of documents, usually using JSON, BSON, or XML format. Each document is a self-contained unit that can contain nested fields and arrays, making it highly flexible for storing semi-structured data.

These systems are ideal for applications where the schema can vary between records, such as:

• Content management systems
• User profile data
• E-commerce catalogs

Popular Document-Based NoSQL Databases

• MongoDB
• CouchDB
• Amazon DocumentDB

Key Features

• Schema-less (no fixed structure)
• Easy to store complex/nested data
• High scalability
• Data stored as collections (like tables) of documents (like rows)

CRUD Operations in MongoDB

In MongoDB, the main operations are:

1. Create (Insert)

Insert a new document into a collection:

db.users.insertOne({
  name: "John Doe",
  age: 30,
  email: "john@example.com"
});

Creates a document in the users collection.

2. Read (Query/Find)

Fetch all users:

db.users.find();

Find users with age > 25:

db.users.find({ age: { $gt: 25 } });

3. Update

Update one document:

db.users.updateOne(
  { name: "John Doe" },
  { $set: { age: 31 } }
);

Update multiple documents:

db.users.updateMany(
  { age: { $lt: 25 } },
  { $set: { status: "young" } }
);

4. Delete

Delete one user:

db.users.deleteOne({ name: "John Doe" });

Delete multiple users with age > 60:

db.users.deleteMany({ age: { $gt: 60 } });

Summary Table