Best practise wanted!
In a datamart (DM) a fact row is linked to a dimension by a dimension ID (key). If a DM is build on top of a (enterprise) datawarehouse (EDW), and the dimension table has a corresponding EDW table with a unique ID (dummy key), will there then be any DM design conciderations for not using that EDW table key.
In other words when you design the DM, should the dimensions then have there own (new) ID's regardless of you allready have modelled (unique) ID in the EDW. I have these considerations in favour for using the EDW table ID keys i a dimension:
1. Staging the DM is easy, the EDW table staging is handling the correctness of the dimension ID's.
2. Backtracing concering DM quality checking, errors and so on, is simplyfied by using the same ID in both DM and EDW.
No. Use the same technical key in DM as in EDW.
If you have a product dimension that is used in several data marts, like sales or production planning, you would like to use the same key in order to consolidate information in these data marts. In SSAS 2000/2005 you can then build cubes with the same product dimension which also means less dimension design and maintenance.
HTH
Thomas Ivarsson
|||Thanks
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