I have been looking at showing sales for the last 'X' months using the brilliant guide from SQLJason. All good so far.
My issue is I would like to also show the sales for the same period last year based on the month I have selected, and include the logic for last 'X' months i.e. in the example below becuase I have selected Dec 2017, only the value for Dec 2016 is showing in the table. I would like my table to show the figures as shown in red going back the same 'X' months and showing BLANK() if no data is available.