Explanation of measure behavior

[BekahLoSurdo]

I am brand new to DAX, can someone please explain this behavior to me? I have two tables:

When I add a Measure to find the sum of Sales, it behaves as I would expect (this will eventually be nested in a longer equation but I'm trying to understand how the building blocks work):

MeasureSalesSum = SUM(Sales[Sales])

But when I add a Measure to find the sum of Budget, it seems to ignore my relationship:

MeasureBudgetSum = SUM(Budget[Budget])

Why is it doing this? I can't seem to find any documentation on Measures working differently for different sides of a One-to-Many relationship. Thank you for helping a brand new DAX coder!

[jrscaletta]

Why you want to do that? You already have the Budget sum. This doesn't have sense in my opinion.

[BekahLoSurdo]

I was trying to simplify it because I found the basic behavior at the center of my issue. The full picture is this:

I need to calculate the difference between the sales and the budget per project. I am using a calculation that works perfectly well when everything is in one table. When the columns are coming from different tables forged by a relationship, however, it does not work because it is duplicating rows for the "One" side of the relationship:

I'd rather not have to move everything into one table as this seems redundant. 

If you can figure out the answer to the simplified original post I can fix the rest, or if you prefer to help with the bigger picture I'd appreciate that as well.

[Anonymous · Accepted solution]

make sure you are using the project column from the budget table as if you use it from the sales table the context cant flow to the budget table and filter it due to the setup of your relationships. You could enable bidrectional filtering but I stronglly recommend that you do not, as you can usually find a way to solve any problem, with out introducing the problems this can create.

And given you are new you do not want to get involved in that yet.

[BekahLoSurdo]

Perfect, thank you!

Yes, I know enough about bidirectional filters to know that I don't know enough yet.

Thanks again.