Agreed with RobertM, there is a place for dates in both tables depending on the business strategy. Imagine if you had the same promotion with a rolling list of products to be discounted (e.g. the "Two for One" promotion that lasts all summer long, but which features a new/different product every week).

As to the person wondering about discount rates, there are pros and cons to that. The pro, as mentioned, is not maintaining a separate list of hard prices. The immediately obvious con is figuring out later, say 6-mos down the road, when products prices' may have changed, just how much that product cost under that promotion.