Joining Factless Fact tables

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Joining Factless Fact tables

Post  sculley on Wed Feb 10, 2010 11:12 am

I am new to BI/Warehousing but have been asked to develop a better reporting system for our software. I am designing a warehouse and seem to have a lot of factless fact tables. There are also many situations where these "fact" tables should be joined together.

One instance is Appointments with Episodes. I have appointments set up as a fact table with about 12 dimensions and have an Episode fact with about 15 dimension. Neither of these tables have any true "facts" other than a simple count. Appointments can have episodes attached, how to I link these and use them for reporting? Do I use a Degenerate Dimension or create an actual "Episode" key? Do I need to set up an entirely new fact table that is a combinaion of episodes and appointments?

Thanks in advance.

Stefanie

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Re: Joining Factless Fact tables

Post  ngalemmo on Wed Feb 10, 2010 5:14 pm

Joining to facts basically involves indiviual aggregate queries (summarized to the same grain) against each fact table with the results joined along common dimensions.

I would not suggest another fact table, but you may want to consider carrying an episode count on your appointments fact table.
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