MERN Stack: MongoDB Introduction

MongoDB Getting Started

MongoDB is a document database and can be installed locally or hosted in the cloud.

MongoDB can be installed locally, which will allow you to host your own MongoDB server on your hardware. This requires you to manage your server, upgrades, and any other maintenance.

You can download and use the MongoDB open source Community Server on your hardware for free.

However we ’ll be using MongoDB Atlas as of now, a cloud database platform. This is much easier than hosting your own local database.

To be able to experiment with the code examples, you will need access to a MongoDB database.

Few steps to get started:

Creating a Cluster

After you have created your account, set up a free "Shared Cluster" then choose your preferred cloud provider and region.

Install MongoDB Shell (mongosh)

Use the official instructions to install mongosh on your operating system.

To verify that it has been installed properly, open your terminal and type:

mongosh --version

Connect to the database

In the MongoDB Atlas dashboard, under "Databases", click the "Connect" button for your Cluster.

Next, choose "Connect with the MongoDB Shell".

Copy your connection string.

mongosh "mongodb+srv://cluster0.ex4ht.mongodb.net/myFirstDatabase" --apiVersion 1 --username YOUR_USER_NAME

MongoDB mongosh Create Database

Create Database using mongosh

After connecting to your database using mongosh, you can see which database you are using by typing db in your terminal.

To see all available databases, in your terminal type show dbs.

You can change or create a new database by typing use then the name of the database.

Create a new database called "blog":

use blog

We are now in the blog database.

The MongoDB Basics: Databases, Collections & Documents | Studio 3T

MongoDB mongosh Create Collection

There are 2 ways to create a collection.

createCollection()
insertOne(object)

You can create a collection using the createCollection() database method.

db.createCollection("posts")

We are here assuming object is a valid JavaScript object containing post data:

db.posts.insertOne(object)

MongoDB mongosh Insert

Insert Documents

There are 2 methods to insert documents into a MongoDB database:

insertOne()
insertMany()

To insert a single document, use the insertOne() method. This method inserts a single object into the database.

db.posts.insertOne({
  title: "Post Title 1",
  body: "Body of post.",
  category: "News",
  likes: 1,
  tags: ["news", "events"],
  date: Date()
})

To insert multiple documents at once, use the insertMany() method.

This method inserts an array of objects into the database.

db.posts.insertMany([ 
{title:“post 1”} ,
{title:“post 2”}
])

MongoDB mongosh Find

There are 2 methods to find and select data from a MongoDB collection:

find()
findOne()

To select data from a collection in MongoDB, we can use the find() method.

db.posts.find( {category: "News"} )

To select only one document, we can use the findOne() method.

This method accepts a query object. If left empty, it will return the first document it finds.

db.posts.findOne( {category: "News"} )

MongoDB mongosh Update & Delete

Update Document

There are 2 methods to update a document:

updateOne()
updateMany()

The updateOne() method will update the first document that is found matching the provided query.

Let's see what the "like" count for the post with the title of "Post Title 1":

db.posts.find( { title: "Post Title 1" } )

Now let's update the "likes" on this post to 2. To do this, we need to use the $set operator.

db.posts.updateOne( { title: "Post Title 1" }, { $set: { likes: 2 } } )

Check the document again and you'll see that the "like" have been updated.

db.posts.find( { title: "Post Title 1" } )

The updateMany() method will update all documents that match the provided query.

Update likes on all documents by 1. For this we will use the $inc (increment) operator:

db.posts.updateMany({}, { $inc: { likes: 1 } })

Now check the likes in all of the documents and you will see that they have all been incremented by 1.

Delete Documents

There are 2 methods to delete documents in MongoDB:

These methods accept a query object. The matching documents will be deleted.

deleteOne()
deleteMany()

The deleteOne() method will delete the first document that matches the query provided.

db.posts.deleteOne({ title: "Post Title 5" })

The deleteMany() method will delete all documents that match the query provided.

db.posts.deleteMany({ category: "Technology" })

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MongoDB - Day 1 of MERN Stack