Question

I am in a situation similar to the one below:

Think for instance we need to store customer sales in a fact table (under a data warehouse built with dimensional modelling). I have sales, discounts related to the sale, sales returns and cancellations to be stored.

Do you think it would be advisable to store sales for a day to a customer in a particular product (when the day is the grain) as a positive value while the returns and discounts are stored as minuses?

Also if a discount is enforced to a customer at a level other than the product (for instance brand), do you think it is alright to persist it with a key particularly assigned to the brand (product is the grain) while the product column being given an N/A, for the particular record?

Thanks in advance.

Answer 1

If your sales are considered a good thing (I’m assuming they are) then recording sales as positive numbers makes perfect sense. Any transaction that reduces sales (i.e. discounts and returns) should therefore be recorded as negative numbers. This will make reporting your sales very natural.

If you have diffent dimensions that might account for a record, you should populate the dimensions that make sense. So yes, attribute a discount to a brand rather than a product if that is what happened in your business transaction. This way your reporting will be able to look at all discounts, at discounts for particular products and discounts for entire brands. If your fact table shows the most direct “cause” of the discount (product or brand) then your reports will be more useful than if you link the fact to brand through a relationship to product.