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basic question, change DIM table

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Post  Filipe Quintieri Wed Oct 29, 2014 8:07 am

Hi

I am new to modeling DW and have basic question.

I have in DIM table Customer some attributes with much change, but these attributes don't have relationship between them.

how do I create scenarios to model this ?

I think to create mini dim com SCD type 2 with relationship between dim customer and mini dim!

what do you think about ?

thanks

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Post  BoxesAndLines Wed Oct 29, 2014 10:09 am

Let me see if I understand your question, you have attributes in your customer dimension that are not customer attributes. In that case, you should remove those attributes and model them appropriately. How you model them is dependent on what those attributes are.
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Post  ngalemmo Wed Oct 29, 2014 12:49 pm

The other way to read it is the attributes themselves are independent of each other. For example, there may be a customer name and a customer status. Both relate to customer but are independent.

This is normal. If you decide to create a type 2 dimension, so be it. You simply create new rows when something changes.

Now, if the problem is that some attributes change very frequently and you don't want to have a lot of customer rows where most of the data is unchanged, you may consider a separate dimension to track the fast changing attributes. But this also means fact tables must reference this dimension as well.
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Post  Filipe Quintieri Thu Oct 30, 2014 3:44 am

For exemple,

Dim Customer
-----------------
PK_Customer
Id
Name
City
Type
....
Active
Locked
DateLastOrder
...

These last three attributes are constantly changing , but not are related to each other .

I think as has been said that a new table with SCD2 is the solution , however I do not see how to connect it directly to the fact table ?

became more clear my doubt ?


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Post  ngalemmo Thu Oct 30, 2014 10:41 am

It would have the same natural key (customer). You would have an additional foreign key on the fact.

I presume 'last order' is not a SCD attribute. Tracking history of the last order in a dimension table makes no sense whatsoever. That is what the fact table is doing.
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Post  Filipe Quintieri Mon Nov 03, 2014 11:51 am

Now I 'm sure what to do .

Thanks for the help.

bye

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