I am facing a strange problem in a chart: I need to show the difference between sales and costs, by month. Now the strange problem is that sales are running sum while costs are puntual per month, so I think that I have to calculate the running sum of costs by month, but month is the dimension of my chart.
here an example of the database:
FEB 2500 (1000+1500)
MAR 3400 (1000+1500+900)
This is driving me mad, thank you in advance for spending time on this, and sorry for my poor english.