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Thread: Discussion Level of grain in fact table

  1. #1
    Join Date
    Mar 2006

    Question Discussion Level of grain in fact table


    I wanted to ask a question about OLAP modeling that applies to mondrian / ROLAP

    After all my years as a BI consulter, I always try to load the fact tables with the most summarized values that is possible, so the Engine does not need to sum/avg/etc on many records... this have been fine until i find my self with many mondrian examples where there is an example that uses the drill through option. So the end client can see that records used to calculate an specific measure member... I believe this is excellent.... but some times on the examples I have seen it goes to level like Order Number, Invoice, etc. so the fact table has all the details.... and to tell you the true.. clients love when they see the can drill to the actual invoices/orders that add to a specific measure.

    So going back to the question... I wanted to start a discussion about this topic and get opinions about the data grain level on the star schema.
    1) Should we always use the low-level detail and use an aggregate_table? so the cube works better.... (Fast performance) / (Drill Through with details)
    2) go directly to the detail (mmmm not like it) but if we do not get to the detail... what is the client going to do with the Drill Through? (Slow Performance) / (Drill Through with details)
    3) Go to the highest level of grain which is the conjunction of all the Dimension end nodes? (Fast Performance) / (Drill Through with high level nodes)

    Well hope everyone understood the topic.. any approaches/opinions?

  2. #2
    Join Date
    Mar 2006


    It seems no on e wants to give opinions about this....

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