...snip

>As to whether or not to use the field in the customer table, well that is a judgement call. Which way makes the system function as it should?

You're asking about the implementation correct? Example, my customer may want to see the YTD figure in the Customer screen. In this case I assume that I would include the field in the customer table so I'm not having to recalculate each Customer's YTD figure as records are navigated via the screen.

However if this is just a figure that shows up in a report, I could stick with good normalization and not have the aggregate field.

Am I following?

>
>Regardless as to whether the YTD Sales figure appears in the customer table or not, the source of the calculation should be the value that is consideredn as the correct one in the case of any discrepancy. The YTDSales field should only be used for the express purpose that you put it there for and for nothing else.

I'm not sure I'm understand your point regarding "should only be used for the express purpose ...and nothing else"