How to compare metrics from different databases?

[Obotchaman]

So I basically want to do what I drew here. I have two databases, one measures two types of expenses within a month and the other is my projection of the expenses. I want to compare them side by side using the stacked chart, but it doesn't seem to allow me to have two different metrics for the same dimention (MONTH). i'm not really sure how to combine the databases either.