In this video we are going to solve the Power BI data modeling challenge
to take any sales which are coming in on a weekend and rolling it over to a weekday. Are you ready now?
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So you are notified whenever I go live to answer your Power BI questions this barbie a challenge is presented by Pelle
From Sweden who is part of the Learn Power BI Family
So Pelle asks that he has this data coming in
Just kinda, you know we can they're not really supposed to have any data apparently
but some data kind of trickles in and what he would like to do is not show these onesies twosies and just
roll it over to the next
weekday and and there was a healthy discussion about this inside the group and there were few options discussed
So let's just walk this through and you're gonna realize that how it might seem like a very straightforward problem
But it's worth it to you know, consider it from the different data modelling perspectives.
So let's look at the very first option, which is we can mess with the data itself
So this is the data coming in in the query editor
so the first thing we can do is and what I'm gonna do is I'm just gonna add a weekday column here so we can
Know what's going on here. Alright, so just for reference I added the weekday here
Now what we could do is change this date column itself. So wherever it says
January 6th, and we detect that it's a Saturday
So whatever we detect a number coming in for a Saturday or Sunday
We could change that date to the next calendar date now we could do that
Although I wouldn't advise to do it. Usually I stay away from
Changing data unless it's it's it's like a real bug which needs to be fixed
So the question to be asked is is there any scenario that you would ask the model that no?
No, I don't want to look at it. Will you fix the date to Monday?
Just show me the original date if that scenario is there then I would strongly recommend not
Changing the column itself. So instead we're gonna take the second approach and we're just going to create a reporting date column
So if we have added a column
during day and we have defined it as
Using the day of the week. So if the day of the week is six or a Saturday
Then we could just gonna add two days to it to make it a Monday make it the next Monday
So 1/6 gives us January 8 and if the day of the week is zero
Which is a Sunday then we just add one day to it right there
And that gives us again January 8 and of course this is gonna apply on every single date. So now we have
Reporting date and the date and let's take it back to our model
So here we have the original
Data as it was coming in and you can see that we had you know
Trickling of data on Saturday and Sunday and and now using a reporting date that data the Saturday and Sunday
You can see is being rolled up
All of this is being sent to January 8th, and that gets the total and that's happening throughout
Whatever you have a Saturday or Sunday
so that works but there's a slight problem which I'm gonna demonstrate so here imagine if we had other
Fields as we do right now in the data set we have da name
Now what happens if I bring in a day name in here?
Well things get really funky
So we had fixed a date January 8th, but the day is still referring to the original date now
Of course, you could it may feel like you need to do a lot more work in this table itself to fix that
But the right way to do it is to have a calendar table
And if you're looking for a calendar table, I have the ultimate calendar table and that's available on my channel
Just look for ultimate calendar download or if you get this file then just click on the link
And that's gonna take you right to it. So
Pretty and pretty much the rule. Is that as as long as you have a single date column?
Then you need a calendar table and it doesn't matter the dates are the month granularity, right?
you only have months or
Even if you only have years I would still strongly
Recommend getting a calendar table and it's so easy to grab that and I'm gonna do that right now and add it to the model
It's just a copy and paste. So now I have the calendar table paste it in and
Using the ultimate calendar table which actually built completely inside the query editor gives you the ultimate
control so you can customize it to
Exact needs and specifications
so a calendar table is loaded and now all we're gonna do is simply connect a
Reporting date to the calendar date and then we can slice and dice our data
Effectively using the reporting date now. Let's see what's going on here
now these visuals were airing out because I had also removed the day of the week Monday and
0-6 that we had in the sales table just because we don't need that anymore
our calendar table has the
weekday and we can have all of that is there so now we have the reporting date and and and we are
connected to the calendar table
Using the reporting date because that's how we would like to see our data and now we can bring in from the calendar we can
Bring in let's say a weekday and it's gonna is not gonna have the weirdness that I was having earlier
So it's just saying Monday and of course in the other scenario, you might even run into trouble for example
Where the month boundary falls across the Saturday and Sunday where let's say March
30th is a weekend
But then you add days to it and that's gonna fall in April and there's gonna be a weirdness there now
of course the big question here
Is that what do you do when you sometimes want to look at data as it was coming in?
Using the original date now
There are two ways to solve this one is using Dax and I'm gonna show that to you really quickly
The other way is called let me I think it's called a role-playing dimension
That's a fancy name, but essentially you get a copy of the calendar table
and you say this calendar is the reporting date calendar and the other calendar is
using the transaction date
Let's say so the way we're gonna solve it though is reporting date is already connected to the calendar table
We're gonna connect this date column to the calendar table as well
Now you notice that it's a dotted line and it kind of tried to auto detect it shouldn't be a bidirectional relationship
I'm just gonna make it a single direction
one to many
Many new one so many on the sales side one on the calendar side
It's almost a little weird so great. But the key thing is that is a
And dotted line really means that that relationship isn't active. It didn't really do anything. Nothing changed
The data is still showing the same way, but now we can go back
and and create a measure which shows us total sales by the
Transaction date, let's do that. So I made a few changes here for one
I changed the date column here to say
Transaction date just to have it really clear and then I redefine a new measure here total sales by transaction date
So this is what I was talking about that all this new measure is gonna do is gonna activate this
Relationship and that's really really easy to do. I'll show you the measure
all this doing is using calculate the magic wand of Dax and say yep calculate total sales, but this time
Activate this relationship based on the transaction date not the default which is active which is by reporting date
Right so default if you just say total sales
Which is the sum of sales amount then we're essentially getting reporting date over here
But now over on this side we have total sales by transaction date so you can see things both ways
You can see yep
This is how we want to report our numbers
But let's say you're debugging exactly trying to find a transaction and you just want to see it by the true
Transaction date that it came in. Then you have that version of the truth as well
now, of course
It's a parent
I was talking about the month boundary and you can see that here in March because these totals are different obviously by day
If you look at January and over here we could see that
January 8th is getting
501 from here so that we saw earlier, but if you would go back to March, let's do that
now you see that March even at the month level total is different because
The month end is falling on the weekend and let's see what's going on over there
So if we drill down into March on both sides again, the left one is transaction date. The right one is the
Reporting date and in the left. What happened was it is the true picture?
This is how the data came in and there was March 31, which is actually a Saturday
They were there were two units there. But what are we gonna do for a reporting date who we gonna push it forward to April?
April 2nd, but yeah, essentially it's gonna roll off of Mars
So when we're looking at by the reporting date it is not gonna be there and that's why the tool is off by 2
So we started off with a seemingly simple question that hey. I just don't want to see this data on a weekend
I just want it to be added to the next date. But really what we have ended up is what's very common in in
Financial reporting where there is a reporting period and there's an actual transaction period and that's often different
So now you have the solution to that
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