MongoDB: Understanding Documents and Collections for Beginners

MongoDB has emerged as a popular choice among developers who lean towards NoSQL databases.

If you dive into MongoDB for the first time, you might encounter some unfamiliar terminologies.

This article is meant to be a beginner-friendly guide where we'll break down two of the most essential terms: documents and collections.


Think of a document as an individual data entry in MongoDB.

This information is grouped in key-value pairs. As an example: { "name": "Alice", "age": 30 }.

If you are used to JavaScript, think of this as an Object.

Each document gets a unique identifier called _id. If you don’t specify one, MongoDB provides it automatically.


If documents are individual data entries, then collections are the folders or containers that hold them.

Typically a "collection" groups related documents. For instance, all data entries about users might be stored in a collection named "Users".

Unlike traditional databases, where each row in a table must have the same columns, MongoDB allows each document in a collection to have its own unique structure.

So, two documents in the same collection can have different keys. For example, a document might have a key for "age", while another might not.

Collections are housed within a database, and there can be multiple collections in a database.

A diagram showing a document collection

If you are familiar with physical filing or even digital file storage, here's an analogy:

  • A MongoDB document is like a single file on your computer.
  • A MongoDB collection is like a folder containing multiple related files.

Happy coding! ✨

Avatar for Niall Maher

Written by Niall Maher

Founder of Codú - The web developer community! I've worked in nearly every corner of technology businesses; Lead Developer, Software Architect, Product Manager, CTO and now happily a Founder.


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