I have a little OLAP system for sales data that I am developing built
from multiple data sources. The problem I have is that one source
only has data summarized by the month. I don't have access to get any
more detail than that. From all our other data sources we have data
down to the transaction. The users would like to be able to drill
down to this level where possible. The only way I can think to set
this up is to create two fact tables, one summarized to the month and
one to the day.

Has anyone else dealt with this type of requirement?