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‫Hey, there. So in this video we're gonna keep

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‫working with the aggregation pipeline.

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‫And I really love this video because

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‫in this one we're gonna solve a real business problem.

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‫So let's imagine that we are really developing

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‫this application for the Nature's Company.

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‫And so let's say that they ask us

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‫to implement a function to calculate

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‫the busiest month of a given year.

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‫So basically by calculating how many tours

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‫start in each of the month of the given year.

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‫And the company really needs this fine tune

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‫to prepare accordingly for these tours,

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‫like to hire tour guides or to buy the equipment

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‫and handle all the stuff like that.

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‫So this is a real business problem

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‫that we now can solve

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‫using aggregation pipelines. Okay?

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‫And so, this is gonna be a real challenge

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‫and I-- I hope it's gonna be really fun

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‫to solve this kind of real business need.

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‫At least if Nature's was a real business, I guess.

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‫So, let's start by

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‫again creating the function.

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‫So export dot and I'm gonna call it:

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‫get monthly plan.

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‫All right.

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‫And again it's gonna be a-- an async function

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‫method, request response or try cache block

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‫and I could actually just have gone and copied it

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‫from up here.

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‫But, nevermind. All right.

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‫And uh now let's actually also uh implement the

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‫route uh right here.

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‫And I'm just gonna duplicate this line

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‫so monthly plan...

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‫And then here this one is called:

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‫get monthly plan. And actually we wanna be able

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‫to pass a year in the URL. And so let's use

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‫a URL parameter for that. All right.

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‫So uh...

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‫coming back here let's start by

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‫uh defining the year.

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‫So the year is coming from req dot params dot year.

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‫Remember that

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‫and then again that trick to transform it

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‫into a number. Okay?

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‫Then I'm gonna create the plan variable

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‫which is gonna await tour dot aggregate.

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‫So just like before and for now

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‫I'm gonna leave it empty here.

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‫And I will copy this piece of code

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‫to then send the results.

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‫And this one is called plan and all right.

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‫So now we're ready to start our aggregation pipeline

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‫just like we did in the last video.

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‫Now to start, let's actually take a look

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‫at the complete results.

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‫Just so we can get a better idea

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‫of what we actually need to build here.

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‫So let's do get all tours and get completely rid

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‫of this query string.

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‫And so here we have all nine tours

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‫and each of the tours, remember, has an array

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‫of these start dates.

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‫So one tour will start on April 25th, 2021.

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‫Then the next one starts on July 20th

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‫and then October 5th. All right.

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‫Then uh the next one has this start date

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‫and all of them I believe have three starting dates.

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‫Okay? So, these dates is what we actually need

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‫as a starting point to create this function

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‫or to create this aggregation pipeline.

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‫Because remember, we want to count how many tours there are

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‫for each of the months in a given year.

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‫And so let's so that we're analyzing 2021, okay?

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‫We have one tour in April, one in July, one in October.

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‫Then let's take a look at the next tour.

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‫Here we have one in June, one in July, and one in August.

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‫So in July we already have two.

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‫So this one and this one.

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‫Next one we have uh, one in March, one in May,

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‫and one in June. So in June we also already have two.

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‫Okay? And so we can keep going and doing it manually

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‫but of course we want to do it with our aggregation.

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‫So if you want to add all of this together

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‫the easiest way would basically be to have one tour

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‫for each of these dates here, right?

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‫And we can actually do that using the aggregation pipeline.

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‫There is a stage for doing exactly that.

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‫And that is called unwind.

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‫So let's use it now and I will then show you

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‫uh-- the result of it and why we really need it.

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‫Okay? So, again we define an object

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‫and then the name of the stage.

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‫And in this case it is: unwind. Okay?

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‫And what unwind is gonna do is basically deconstruct

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‫an array field from the info documents

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‫and then output one document for each element of the array.

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‫And so that's what I was saying before.

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‫Which is, that basically we want to have one tour

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‫for each of these dates in the array. Okay?

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‫And this stage can be really useful for so many cases.

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‫So, the field with the array that we want to unwind

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‫is start dates.

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‫All right and so for now that's actually all.

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‫So I just want to show you the result of that right now.

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‫And I think we already actually have everything in place

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‫for this to work. So just keep in mind

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‫that the route is called monthly plan and then with a year.

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‫Which for now it's not gonna have any results

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‫but um, we have to define it anyway.

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‫So monthly plan and the year of 2021.

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‫So let's send this now.

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‫And indeed we now have uh this start date

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‫no longer as an array but only this first element

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‫of the array that we had before.

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‫Let's put them side-by-side. And so you see, we had

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‫or actually let's do it with the first one.

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‫So we had the first taker for April 25th,

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‫July 20th, and October 5th.

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‫And so now we have the first hiker on this date here,

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‫then we have the first hiker on uh, July 20,

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‫and now we will have the first hiker for October 5th.

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‫So, exactly the result that we wanted

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‫because now we have one document for each of the dates.

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‫Okay? So instead of having nine, we now have 27

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‫which is nine times three. All right.

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‫So, that's the first date. Now let's actually go ahead

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‫and select the documents for the year that was passed in.

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‫Okay? And remember which stage we use for that

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‫that's right, we use match.

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‫So remember, match is basically to select documents.

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‫So just to do a query.

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‫And so the year is in the start dates.

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‫So start dates is the one that we're gonna search for.

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‫So start dates, and now what do we want?

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‫Well we want the--the date basically to be greater

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‫than January 1st of the current year,

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‫so let's say 2021. And we want it to be less

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‫than January 1st of 2022, all right.

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‫So basically we want it to be 2020 and 2022. All right?

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‫So let's put that in code now.

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‫So start dates and then we need another object

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‫for the operators. So, greater or equal than

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‫and in MongoDB this works perfectly fine with dates.

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‫So Mongo is actually perfect for working with dates like

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‫doing date comparisons. So it works really great.

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‫So now we actually need to define a new date here

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‫so that, that one can then be compared with the date

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‫that's in each of the documents.

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‫So the formula of the date is year, month, and date.

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‫And so let's do a template string here

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‫and use our year variable.

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‫So January 1st.

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‫So, we want our date to be greater or equal than

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‫January 1st, 2021 and let's actually write that here

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‫just to keep it in mind. And we want it to be less

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‫less than, or we can say less than, equal.

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‫Let's go ahead and copy this one and then

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‫December 31st. Okay? So, basically we want it to be between

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‫the first day of the year and the last day

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‫of the current year. Okay?

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‫So let's keep testing it, so I will test it now

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‫after each of the stages. So sending this

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‫and now we should have only tours here that are in 2021.

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‫So let's confirm that 2021, here as well, here as well,

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‫here as well.

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‫Mm, so you see we really have no other year. Right.

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‫It's always 2021. Okay? So I think we've seen enough.

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‫And so, let's go back. Next up is where the magic happens.

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‫And so that is usually in the group stage.

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‫So let's add the group here, so just like before

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‫so group and remember we need to specify the ID field

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‫basically to say what we want to use to group our documents.

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‫Now we want to group them by the months, right?

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‫But currently we simply have the entire date,

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‫with the year, the month, the date, and even the hour.

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‫So I guess it's 10 in the morning or something.

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‫But again we only want the month. So let me show you

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‫just another like magical MongoDB operator.

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‫So, where is that? So, here, back in this reference here

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‫we actually have a couple of aggregation pipeline operators.

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‫And it's in here where we have this really handy uh

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‫date operator. So let's take a look at this.

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‫And the one that we're gonna use is month.

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‫So it returns to month for a date as a number.

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‫And so this will basically extract the month

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‫out of our date. And there are lots of other operators.

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‫Like this for example, we could even calculate the week

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‫or just the year, okay?

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‫But the week could also be very handy.

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‫But let's uh, let's keep it with the month. All right?

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‫So again, you can take a look at these uh--

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‫special aggregation operators.

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‫Because there are a ton of them, as you see here.

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‫Okay? So actually these operators that we're using here

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‫in the aggregation pipeline are uh, yeah exactly that.

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‫They are aggregation pipeline operators.

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‫We have stages and then operators that we can use. Okay.

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‫And in this case, again, we use the month.

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‫And then again the name of the field,

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‫where we want to basically extract the date from.

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‫All right, give it a save, then that error disappears, okay.

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‫So we are grouping it now by the month.

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‫And now the real information that we want

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‫for each of the month is how many tours start in that month?

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‫Right? And for that all we're gonna do is basically count

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‫the amount of tours that have a certain month, right?

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‫So num of tours starts.

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‫And so this one is actually

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‫very similar to what we did before.

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‫So we use add and then for each of the documents

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‫we add one. So just like we did before.

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‫But actually it is sum and not add, okay so just like here

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‫when we counted the tours for each of the difficulties

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‫we simply added the number one for each of the documents.

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‫And so here we do the same.

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‫All right, so let's again test this.

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‫And we're getting really close already to our end result.

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‫And indeed, here we go. So we have February with one tour.

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‫December with one tour, we have November or actually

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‫September with two tours.

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‫And then we have two tours in all of this in here

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‫actually we have three tours in July.

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‫So this is getting pretty close to our result.

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‫So that's absolutely fantastic.

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‫So this part here, which I think was the most difficult one

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‫is already working.

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‫All right.

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‫Now we actually want some more information

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‫which is not only how many tours

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‫but also which tours? So let's do that.

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‫So if you want information about which tours

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‫that should actually be an array.

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‫Right? Because how else would we specify

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‫two or three different tours in one field, right?

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‫And so basically we want to create an array

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‫and we do that by using push

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‫and then what we're gonna push into that array

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‫as each document goes through this pipeline

242
00:13:57,660 --> 00:13:59,853
‫is simply the name of the document,

243
00:14:02,010 --> 00:14:05,920
‫or actually the name field. So not the name of the document

244
00:14:05,920 --> 00:14:07,440
‫but the name field.

245
00:14:07,440 --> 00:14:12,113
‫So in this case the name of the tour. Okay so let's test it.

246
00:14:13,520 --> 00:14:15,380
‫And...

247
00:14:15,380 --> 00:14:17,870
‫bam, here we go!

248
00:14:17,870 --> 00:14:22,430
‫So we have also now the name of the tours in there.

249
00:14:22,430 --> 00:14:26,370
‫So fantastic. Let's see, yeah. Here we have all the three.

250
00:14:26,370 --> 00:14:29,560
‫Next up, let's actually uh change the name

251
00:14:29,560 --> 00:14:31,690
‫of this field here, okay?

252
00:14:31,690 --> 00:14:34,760
‫Now not really change but we're simply gonna add

253
00:14:34,760 --> 00:14:37,660
‫another field which will have the same value here

254
00:14:37,660 --> 00:14:41,363
‫so that later on we can basically delete this ID.

255
00:14:42,400 --> 00:14:46,450
‫Okay, and so for that we're gonna use the next stage

256
00:14:46,450 --> 00:14:48,313
‫which is called: add field.

257
00:14:50,490 --> 00:14:52,640
‫So add field and this one

258
00:14:52,640 --> 00:14:56,290
‫is pretty straight forward. It simply does what it says.

259
00:14:56,290 --> 00:14:59,990
‫So add field is used to add fields and actually it is

260
00:14:59,990 --> 00:15:01,980
‫called add fields.

261
00:15:01,980 --> 00:15:06,864
‫And so now, the name that we want to add or the field

262
00:15:06,864 --> 00:15:11,330
‫is called month and it has the value of

263
00:15:11,330 --> 00:15:13,463
‫the field with the name ID.

264
00:15:15,060 --> 00:15:17,670
‫All right. So, pretty straight forward

265
00:15:17,670 --> 00:15:20,300
‫simply the name of the field and then the value.

266
00:15:20,300 --> 00:15:24,670
‫Which as usual, we need to use the uh the dollar sign.

267
00:15:24,670 --> 00:15:27,870
‫All right, just to test it again.

268
00:15:27,870 --> 00:15:29,413
‫Indeed now we have the month.

269
00:15:30,500 --> 00:15:33,630
‫Then next up, let's actually get rid of this

270
00:15:33,630 --> 00:15:34,793
‫and so we use project.

271
00:15:38,860 --> 00:15:43,090
‫So I'm really trying to put as many stages in here as I can

272
00:15:43,090 --> 00:15:45,930
‫to-- to show you really everything I can.

273
00:15:45,930 --> 00:15:49,460
‫So how does project work? Well we simply give

274
00:15:49,460 --> 00:15:53,130
‫each of the field names a zero or a one.

275
00:15:53,130 --> 00:15:57,900
‫So let me show that to you. So we can say ID

276
00:15:57,900 --> 00:16:00,960
‫and set it to zero. And that will then make it so

277
00:16:00,960 --> 00:16:05,130
‫the ID no longer shows up. If I put a one here, well,

278
00:16:05,130 --> 00:16:08,160
‫then it would actually show up, okay?

279
00:16:08,160 --> 00:16:12,140
‫So this one I'm not gonna test. Let me just add the next one

280
00:16:12,140 --> 00:16:17,140
‫which is the sort one which I believe I used it before

281
00:16:17,440 --> 00:16:20,783
‫but still I want to sort it here by the number or tours.

282
00:16:21,640 --> 00:16:26,120
‫Okay, so right now it's not 100% useful we are still missing

283
00:16:26,120 --> 00:16:29,410
‫because we should actually sort it by uh, really by the

284
00:16:29,410 --> 00:16:30,820
‫number of tour starts.

285
00:16:30,820 --> 00:16:35,260
‫So the name of the field is number of tour starts

286
00:16:35,260 --> 00:16:39,290
‫and uh remember we had one before which was for ascending

287
00:16:39,290 --> 00:16:42,140
‫and minus one which was for descending and of course

288
00:16:42,140 --> 00:16:43,220
‫that's what we want.

289
00:16:43,220 --> 00:16:45,893
‫So starting with the highest number.

290
00:16:48,220 --> 00:16:53,220
‫So it should be three in our case and yeah, it is.

291
00:16:53,870 --> 00:16:57,720
‫So July is the busiest month with three tour starts

292
00:16:57,720 --> 00:17:01,440
‫the Forest Hiker, the Sea Explorer, and the Sports Lover.

293
00:17:01,440 --> 00:17:02,944
‫Okay, so this is kind of done.

294
00:17:02,944 --> 00:17:06,710
‫Let me just show you one, uh last stage here

295
00:17:06,710 --> 00:17:09,540
‫which is uh, not really helpful here

296
00:17:09,540 --> 00:17:11,560
‫but I wanted to show it to you anyway.

297
00:17:11,560 --> 00:17:15,210
‫So we have the limit, and this one is exactly the same

298
00:17:15,210 --> 00:17:19,110
‫as limit in uh query. So basically it is gonna allow us to

299
00:17:19,110 --> 00:17:21,880
‫only uh, have six documents here.

300
00:17:21,880 --> 00:17:23,763
‫Okay so basically six outputs.

301
00:17:25,160 --> 00:17:29,530
‫Okay so let's test that, and so now indeed

302
00:17:29,530 --> 00:17:30,650
‫we should only have six.

303
00:17:30,650 --> 00:17:35,160
‫One, two, three, four, five, and six. All right.

304
00:17:35,160 --> 00:17:39,150
‫Again, not really useful because that's uh gonna cutoff

305
00:17:39,150 --> 00:17:42,670
‫the six least biggest month, which we don't want.

306
00:17:42,670 --> 00:17:44,800
‫So let's simply set it to 12 here,

307
00:17:44,800 --> 00:17:49,010
‫just so we can leave it here as a reference for you.

308
00:17:49,010 --> 00:17:54,010
‫All right, so one more time but it, uh should be working now

309
00:17:54,470 --> 00:17:58,122
‫and the real business problem is now solved.

310
00:17:58,122 --> 00:18:01,400
‫And I know this is quite a lot of moving pieces

311
00:18:01,400 --> 00:18:04,150
‫that we have here. A lot of different stages.

312
00:18:04,150 --> 00:18:07,930
‫And so I know it's a lot for you to take in at this moment.

313
00:18:07,930 --> 00:18:10,670
‫But don't worry, you don't have to know all of this stuff

314
00:18:10,670 --> 00:18:12,170
‫all at the same time.

315
00:18:12,170 --> 00:18:14,970
‫With practice you will keep improving

316
00:18:14,970 --> 00:18:17,740
‫and you will know when to use which of the tools

317
00:18:17,740 --> 00:18:19,610
‫that you have at your disposal.

318
00:18:19,610 --> 00:18:22,220
‫Just keep in mind that you can always read the documentation

319
00:18:22,220 --> 00:18:25,840
‫which is kind of complete and really great learning material

320
00:18:25,840 --> 00:18:28,120
‫besides this course, okay?

321
00:18:28,120 --> 00:18:29,970
‫And that applies to all of the technologies

322
00:18:29,970 --> 00:18:31,140
‫that we're learning here.

323
00:18:31,140 --> 00:18:35,320
‫So I really encourage you to always study the documentation.

324
00:18:35,320 --> 00:18:39,220
‫And I know it can be really frightening to look at it

325
00:18:39,220 --> 00:18:42,390
‫and without this course it would be a lot more difficult

326
00:18:42,390 --> 00:18:44,240
‫to learn from the documentation

327
00:18:44,240 --> 00:18:46,270
‫but with this really good starting point

328
00:18:46,270 --> 00:18:49,200
‫that you get in these videos it's then a lot easier

329
00:18:49,200 --> 00:18:51,230
‫for you to keep learning more and more uh,

330
00:18:51,230 --> 00:18:54,220
‫using that documentation, okay?

331
00:18:54,220 --> 00:18:57,610
‫So I wouldn't expect you to solve this challenge

332
00:18:57,610 --> 00:19:01,180
‫on your own of course, which is why we basically

333
00:19:01,180 --> 00:19:03,170
‫did it together here, right?

334
00:19:03,170 --> 00:19:05,760
‫But I hope you had as much fun as I did

335
00:19:05,760 --> 00:19:10,030
‫because again, I really love to solve this kind of problems

336
00:19:10,030 --> 00:19:11,810
‫it's-- it's really fun I think.

337
00:19:11,810 --> 00:19:14,280
‫But anyway, enough talking now.

338
00:19:14,280 --> 00:19:16,880
‫In the rest of the section we will now talk about

339
00:19:16,880 --> 00:19:20,130
‫a couple of uh, other features we have available to us

340
00:19:20,130 --> 00:19:23,283
‫in Mongo, so that should be pretty fun as well.