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Recursive hierarchies or non recursive, pros and cons

Recursive dimensions in SSAS 2005 is supported only in the form of parent-child dimensions. You can check my previous entry about parent-child dimensions but shortly they rely on a single parent at the top of the dimension. The more complex form of recursive hierarchies allows several parents at the top and are called Bill Of Materials hierarchies. The later is not supported in SSAS 2005 unless you model it as many-to-many dimensions.

Lately I have met some developers that prefer to use parent-child hierarchies as a standard structure for all dimension in a data warehouse and in SSAS 2005. Even if Microsofts advice is to be careful with parent-child dimensions, like you can read in the SSAS 2005 "Performance Guide", some developers thinks that this is valid design approach. Still they will never build a recursive hierarchy of the time dimension because even they know that you need named dimensions levels, like Year, Month and Date, in order for time calculations to work.


Tags: parent-child


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