I have recently got familiar with the concept of “Factless Fact Tables”, and due to the fact that it was very interesting for me, I like to share it with you, if you are not already familiar with it.
The “Factless Fact Table” is a table which is similar to Fact Table except for having any measure; I mean that this table just has the links to the dimensions. But what is the benefit?
These tables enable you to track events; indeed they are for recording events.
Another kind of this Table is known as “Factless Coverage Table” which is very usefull. Imagine that you have a retail stores and each store has its own promotion policy. It would be very complicated if you wanted to answer this sort of question: “Which products were on promotion that didn't sell?”
The best way for covering these kinds of questions is the coverage tables. These tables hold the coverage data for answering these questions.
I also recommend reading “Factless Fact Tables” that was written by Ralph Kimball.
7 comments:
Usefull post Amin!
I add an extra info... FactLessTable does not have measures and MUST has a link to a Time Dimension. Stores a relation between 2 dimensions in at a moment in time.
Cheers my friend!!
Pedro
Dear Amin,
As you wrote about FactTables types, would be very interesting if your describe the different dimensions following Kimball approche like conformed dimension... what you think?! :-) We need to see you blogging!!! Cheers friend!!!
Thanks Amin and happy new year! :-)
Cheers!!!
Dear Amin,
As you wrote about FactTables types, would be very interesting if your describe the different dimensions following Kimball approche like conformed dimension... what you think?! :-) We need to see you blogging!!! Cheers friend!!!
March 21, 2008 6:41 PM
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Dear Pedro,
It is a good idea, and I am going to write a new post for conformed dimensions.
Thank you.
Regards,
Amin
March 23, 2008 11:37 PM
Is it possible to create a fact table which is hybrid of factless attributes and additive measures?
Cheers...
Dear Darshil,
I couldn't imagine a situation in which we need such a solution, because factless fact tables are usually about the relation that has not happened yet, so there should not be any measure for the action that has not happened yet.
if you could provide an example, it would be much easier.
Regards,
Amin
Nicely explained in few words.
Thank you
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