Introduction to MongoDB

MongoDB is a document database — instead of rows and columns in fixed tables, it stores data as flexible, JSON-like documents grouped into collections. It is the most widely used database in the NoSQL family, and it pairs naturally with JavaScript and Node.js, since a MongoDB document and a JavaScript object are shaped almost the same way.

In a relational database (see this site's SQL course), every row in a table must have the same columns. In MongoDB, every record — called a document — is its own self-contained JSON-like object, and different documents in the same collection can have different fields:

If you already know SQL, most concepts have a direct MongoDB equivalent — the words are different, the underlying idea is close enough to reason from.

MongoDB tends to suit data that is naturally nested or that changes shape often — a user profile with an arbitrary list of addresses, a product catalog where different product types have different attributes, an activity log where every event has different fields. A relational database still tends to win when data is highly structured and relationships between tables matter a lot — accounting ledgers, inventory systems with strict foreign keys, anything where you would lean hard on SQL JOINs and transactions.

This course goes from installing MongoDB through every core CRUD operation, schema design decisions, indexes, the aggregation pipeline, and finally connecting a real Node.js application to MongoDB using both the official driver and Mongoose.