Intro to NoSQL

Objectives

Describe how Mongo databases came about & why they're useful
Compare and contrast NoSQL with SQL
Define what a document is in the context of MongoDB
Explain the difference between embedded and referenced documents, and how we use each to model relationships in MongoDB
Issue basic CRUD commands to a database from the Mongo Shell

What is MongoDB?

MongoDB (short for humongous) is one of the new breeds of databases known as NoSQL databases. NoSQL databases are heavily used in realtime, big data and social media applications and generally called NoSQL because they do things a little differently than traditional SQL databases. It is a schemaless document-based datastore. This means it doesn't have tables. It instead has documents.

Data Format

A MongoDB database consists of documents.
A document in MongoDB is composed of field and value pairs.

{
  _id: ObjectId("5099803df3f4948bd2f98391"),
  name: { first: "Alan", last: "Turing" },
  birth: new Date('Jun 23, 1912'),
  death: new Date('Jun 07, 1954'),
  contribs: [ "Turing machine", "Turing test", "Turingery" ],
  views: 1250000
}

What does this data structure remind you of? JSON!

A MongoDB document is very much like JSON, except it is stored in the database in a format known as BSON (think - Binary JSON).

BSON basically extends JSON with additional data types, such as ObjectID and Date shown above.

Read more about MongoDB here: MongoDB Documentation

MongoDB vs. Relational Databases

Key Differences of MongoDB

Schema-less The documents in a MongoDB collection can have completely different types and number of fields from each other. How does this compare to a SQL database like PostgreSQL?
No Table Joins In a SQL DB, we break up related data into separate tables.

In MongoDB, we often embed related data in a single document, you'll see an example of this later.

The supporters of MongoDB highlight the lack of table joins as a performance advantage since joins are expensive in terms of computer processing.

MongoDB