SSAS: Can I make my Distinct Count totals subtotal correctly?
I've seen this question come up a couple of times. What is usually being asked is "can we make the subtotals additive for a distinct count measure?" – and the short answer is a resounding No!
But the short answer does not really make for a compelling blog post, so let's dig a little deeper into this issue. The more complete answer is that while there are some techniques that can make a distinct count "appear" to be additive in some circumstances, they are fundamentally flawed and will produce inconsistent results as distinct count measures are inherently non-additive.