Lesson 6 - First steps in MongoDB

In the previous lesson, Introduction to MongoDB, we installed the MongoDB database and connected to it. Today we're going to get a little familiar with it. We'll explain the basic concepts and learn to write data and read it back. We'll also work with the Mongoose package and explain what a schema and model are.

Recapitulation

Last time we installed the Mongoose package into a new project. Mongoose will provide us with an API to make the work with Mongo easier. At the same time, we wrote a simple script to connect to the database:

mkdir mongo-project
cd mongo-project
npm init --yes
npm install mongoose

And index.js looked like this:

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/moviesdb', { useNewUrlParser: true })
  .then(() => console.log('Connected to MongoDB!'))
  .catch(err => console.error('Could not connect to MongoDB... ', err));

Terminology

MongoDB stores data in collections (we can say that collections correspond to tables in the SQL databases - if you don't know SQL, imagine an Excel spreadsheet). Individual records in a collection are called documents (they correspond to the rows of a traditional database's table). And individual items of each document (something like table columns) are fields. Does it make sense? Okay, let's go!

Schema

In Mongoose, we use a schema to define the structure of our documents. As the official Mongoose documentation says, "everything in Mongoose starts with a schema." The schema is specific to Mongoose, Mongo itself has no such thing (last time we said Mongo is schema-less). Let's prepare a simple schema for our movie database: