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In the last section we had a very long discussion about how we would be using lot to uniquely identify

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users inside of our application.

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In this video we're now going to continue by talking about the basics of Mongo D-B and then in the next

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section we will start to wired up inside of our application.

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Once we have Lango D-B set up inside of our application we can then make sure that we create a new user

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record every time someone signs into our application using cloth.

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After that we can then get back into our waterflow making sure that we deal with this cookie thing and

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all that kind of associated logic that we will make sure to review over time.

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So let's get to it.

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Let's start talking about the basics of Monga.

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We're going to start by reviewing a diagram that we are looked at much earlier inside this course.

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But with one small change to it.

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So we had previously looked at this diagram where we had said that we have our re-act up running inside

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the browser and no we haven't done this yet but we will very shortly.

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We had said at the re-act up would communicate with our express API by exchanging age TTP requests that

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contain little snippets of Jason data we haven't previously said that express would interact with our

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Mongo divi database to store records and pull out existing records.

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Now I've made one change to this diagram where I've added in the additional box here for a library called

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mongoose J.S..

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Mongoose is a optional library that we are going to be using inside this course.

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The sole purpose of mongoose is to make our lives easier when working with Mongo D-B.

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So again it is completely optional.

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In general it is required in this course but in general it is optional but I highly recommend you use

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it because it wraps up a lot of very common operations that you might have to do by hand when working

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with Mongo.

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So as we start to talk about Mongo inside of this course we're really going to be covering two separate

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and distinct topics.

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On the one hand we will be talking about Mongo D.B and on the other hand we will be talking about mongoose

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and how we use it to interact with the data that sits inside of Lango.

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OK.

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So let's start that process now.

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The first thing we're going to discuss is how Mongo internally stores information.

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So here's Monga.

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Mungo internally stores records into different collections every different collection that sits inside

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of our database can have many different records and we can have many different collections.

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So inside of one Mongo divi instance we might have a collection of users a collection of posts and a

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collection of payments inside of a single collection like let's say the users collection.

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We have many different individual records in the context of a user's collection.

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We might imagine that every single one of these records represents someone who has signed in or signed

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up to our application.

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So we've got one record that represents a user with the name of Anna and another record that represents.

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Alex bill and so on every single record is essentially a little piece of Jaison or essentially a plain

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javascript object.

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In other words every single record is a collection of key value pairs.

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So I can have a name property with a value of Anna.

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And let's zoom in here really quick a height with a value of 150.

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And then in the next object over or the next record over I might have an ID a name and an H.

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One of the important defining characteristics of Mongo D-B is the fact that it is what we refer to as

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being schema Elance.

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In other words inside of one single collection every record can have its own very distinct set of properties.

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So you'll notice that for example this first record right here has a height property but the second

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one doesn't nor the third but the fourth one does likewise.

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The second record right here has an age property but no other record in here does.

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This is in direct contrast to traditional databases like siecle type databases or relational databases

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where traditionally every single record has to have the exact same properties.

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So in other words everything would have to have an ID a name a height an age defined so that is one

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distinct difference that separates Mungo DVH from other databases like say My sequel or postscripts.

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And let me be clear One difference among many many other differences as well.

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OK.

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So that is a little bit into the background of Mongo D-B.

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Remember we have many different collections in every collection has many different records.

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You can think of every record as being a single javascript object that has a couple of different key

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value pairs.

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Now the next thing I want to talk to you about very briefly is what Mongoose is doing for us.

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So we're going to first talk a little bit about exactly how mongoose relates to Mongo D-B So on the

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bottom half of this diagram will focus on this bottom half.

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First we had just one second ago said that in Lango D-B we have a bunch of different collections and

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every collection has a bunch of different records to represent this type of structure in the javascript

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world or in the expressed code or the no J.S. code that you and I are going to write.

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We are going to have two different very important concepts that are implemented by Munger's.

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So just to be clear these are like mongoose things up here.

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Let me label this as being like this is from mongoose.

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So in the mongoose world or by using the mongoose library we make use of something called a model class

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a model a class created with Mongoose represents an entire Mongo DB collection.

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So the model class is used to access a single collection sitting inside of Mongo D-B the model class

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has a bunch of functions attached to it that are designed to work with an entire collection.

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And so doing things like say creating a new record or searching all the records inside of our collection

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is done by using a model class.

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Mongoose also gives us access to something called Model instances.

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And so to be clear again this is all from mongoose model.

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Instances are all javascript objects that represent a single record sitting inside of a collection.

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So in practice we end up with one modeled class representing one collection inside of Mongo DVH and

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then we end up with many instances each of which representing one of the records inside of our Mago

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DVD collection.

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So again one more time because this is a very important distinction.

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One class is related to one collection we have a bunch of instances each of which represent one individual

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record.

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OK.

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So I think there might be one more slide here.

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No that's about it.

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So I think that's enough for a very quick introduction to Mongo and mongoose.

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Now I do want to tell you right now that inside like the first half of this course we're not really

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going to using mongoose in Lango a tremendous amount.

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So right now we're going to go through a little bit of the basic set up and we're going to use it in

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a very limited basic way but later on in the course like in the last quarter we're going to come back

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to Mongo and we're going to talk about many more topics around it so as to make sure we're on the same

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page about what we're talking about when.

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OK.

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So I think this is enough the introduction.

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Let's take a break.

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We're going to come back in the next section and we're going to start to set up our Mongo DB database.