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harithay
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Post Posted: Tue Dec 21, 2004 1:05 pm Reply with quote    Back to top    

Where would you use a factless fact table
mhester
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Post Posted: Tue Dec 21, 2004 1:48 pm Reply with quote    Back to top    

Factless fact tables come in two (2) varieties. -


    Record/track an event
    or
    Coverage tables



Most of the time a factless fact table does not contain any data other than key fields. No numeric additive data. One variety of a factless fact might record or track an event. Another factless fact table is the coverage fact table and you would use this when the main fact table in the middle of your dimensional model contains sparse or non existant data.

This is pretty much right out of many of Kimball's books and website. You can do more research by either surfing the web or reading the books.

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kduke

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Post Posted: Tue Dec 21, 2004 4:56 pm Reply with quote    Back to top    

I have seen factless facts used mostly to report on all salesmen regardless if they have sales or some simliar concept. This way you can see the salesman has no sales for a given time period and the r ...

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mhester
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Post Posted: Tue Dec 21, 2004 5:02 pm Reply with quote    Back to top    

Kim gives a great example and one that certainly typifies what a factless fact table is used for. It really is nothing more than the counting of an event.

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roy

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Post Posted: Sun Dec 11, 2005 9:01 am Reply with quote    Back to top    

pump307,
What exactly did/do you mean?

pump307 wrote:
OMG u'r such a n00b. go sit in the corner and be ashamed of yourself. Evil or Very Mad Mad

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kcbland

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Post Posted: Sun Dec 11, 2005 9:02 am Reply with quote    Back to top    

pump307 appears to be a robot spamming content on random postings. Better boot that user off.

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datastage
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Post Posted: Wed Dec 28, 2005 1:02 pm Reply with quote    Back to top    

kduke wrote:
I have seen factless facts used mostly to report on all salesmen regardless if they have sales or some simliar concept. This way you can see the salesman has no sales for a given time period and the reports will reflect that. Otherwise the salesman does not show up at all on the report.


Kim or Mike (or someone else),

could you give some more detail or more examples. I think I understand factless facts, but with the example of sales I'm envisioning a fact with a numeric value of 0, which should show up with a good reporting tool and I don't this think qualifies as a factless fact, so perhaps another example would provide more clarity.
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kduke

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Post Posted: Wed Dec 28, 2005 2:18 pm Reply with quote    Back to top    

That is correct. All measures are 0. You can do the same with an outer join to the salesman dimension but sometimes this messes up OLAP tools. The purpose is to show all salesmen even if they had no s ...

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ray.wurlod

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Post Posted: Wed Dec 28, 2005 3:06 pm Reply with quote    Back to top    

From The Data Warehouse Lifecycle Toolkit by Kimball et al (pages 212-216 in the 1998 edition): Factless fact tables are the preferred method for recording events in a data warehouse where ...

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wnogalski


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Post Posted: Thu Dec 29, 2005 9:40 am Reply with quote    Back to top    

If a fact record has a 0 value it doesn't mean that this is a factless fact - it's possible that in this particular case f.e. the daily sales was 0 but normally you're able to measure the fact (and that's why this isn't a factless fact).
The best definition is the one in Ray's post and as far as I remember there's some more on that topic in Kimball's books and on his website.

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