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Former Member

Large dimension tables

I am trying to get a grip with how a dimension table can have more records than the fact table since the key for the dimension table is DIMID. Can someone give me a practical example? Thanks

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  • author's profile photo Former Member
    Former Member
    Posted on Nov 21, 2007 at 08:45 AM

    Niten,

    If the dimension table have chars whose relation is m:n and not 1:n, then the dimension tables will have more records. Suppose you take a document number, assume that lakhs of documents are created everyday. Then the dimension obviously increases. If some other chars are there with document number the dimension table size iincreases gradually which is not good for performance.

    In such a case, you make document number as a line item dimension.

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    • Former Member Former Member

      Thanks Venkat, I am still not clear.

      Pre step 4 I have 1000 DIMID which represent all records in the fact table since it is the first load

      Post step 4 I have 200 transactions which are on a different calendar day so 200 new dimids generated in terms of time (correct)

      Post step 4 for Dimension 4 I have 50 DIMIDs which represent the SID combination and 150 which are not represented so for these there would be 150 dimids generated is that not the case and if not could you explain why

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