Last image of Historical Data

Hello,

I have a slowly changing dimension Sales Person of type 2, where I am keeping history of the sales person Unit, Region, and Sales Channel which are attributed on the Sales Person dimension.

The client is requesting to be able to report on the Sales Person last image, for example if the last image Region of this sales person is Region X, then all the portfolio of this Sales Person should now be linked to Region X irrespective of what it was historically. At the same time, we should be able to report on the production done by region as it occured historically.

To my kowledge, my design would allow to report on production historically but not the last image. I read about an article that suggested to create additional attributes in the dimension (i.e. Current_Region, Current_Unit, ....) and thus for each row I will have two values for each historical attribute. Then, in order to produce the report for last image i will use the Current_ attributes that are being updated whenever a new image arrives.

I am not sure if this is a proper solution to duplicate the columns.

Would be glad to hear out any suggestions and opinions regarding this design issue.

Thanks in advance,

Grace

Hi! This is a common problem in data warehouse design and known as the slowly changing dimension(SCD) problem.

The approaches to solve this is normally outside of SSAS2005 and an ETL/DW problem:

-Type one: Overwrite all attributes/columns with the current value (This is the one you are suggesting)

-Type two: Put a timestamp on dimension members when a an attribute changes, that you would like to keep an history of. You will have to use surrogate keys for each member and version of the dimension keys to use this approach.

-Type tree: Add a new column for the attribute that you would like to keep history for.

The better approach is to separate attributes in different dimensions tables that have a dynamic relation and enter a new dimension key in the fact table. Separate geography from customer. Never have a key account or salesperson attribute in your customer table, because these relations change over time.

Have a look at www.kimballgroup.com for more information.

HTH

Thomas Ivarsson