Databases & Collections

What is a Database?

In the MSSQL universe, we have a Database. Good news: In MongoDB, we also have a Database.

• SQL Database: A container for tables, views, stored procedures, etc.
• MongoDB Database: A container for collections.

Switching Databases

When we first connect, we land in a default database (like test). To start working, we need to switch into our specific database universe.

We use the use command to switch contexts.

use node2know

We should see: switched to db node2know.

Lazy Creation

The database doesn’t technically exist yet. MongoDB utilizes Lazy Creation. The hallway isn’t built until we put a box in it.

What is a Collection?

Now that we are inside our node2know database, we need a place to store data.

In the MSSQL universe, the closest analog to a Mongo Collection is a Table.

• SQL Table: A rigid structure with defined columns and types.
• MongoDB Collection: A flexible container for documents.

The key difference? A collection is Schemaless by default. In a SQL table, every row must follow the same rules (columns). In a MongoDB collection, every document can have a completely different structure if we wanted (though for sanity, we usually keep them similar).

The Explicit vs. Implicit Approach

Option A: Implicit (The Cowboy Way)

Just insert a document into a collection that doesn’t exist, and MongoDB will create it for us.

db.users.insertOne({ name: "Solo" });

Fig 1: Inserting a document into a collection that doesn’t exist.

Option B: Explicit (The Architect Way)

We can create a collection manually if we want to set specific rules (validation, capped size, etc.).

db.createCollection("students");

For our purposes, we will stick to the Architect Way to be intentional.

db.createCollection("projects");

Verify it exists:

show collections

Fig 2: Show collections.

⏭ Inserting Documents

Stashing our first digital assets using insertOne({}) and insertMany([]).