Time Dimension

[eldonp]

Odata warehouse started in 2002 so the first date in the date dimension has been 01/01/2002 with a surrggate primary key of 1. Now we have to integrate other data into the data warehouse. The date dimension needs to be updated with dates back to 1994. Numerous fact tables have been created. What is the best practice for updating the date dimension? Should I have the surrogate primary key go into negative values or make 01/01/1994 the first date and update the fact tables?

[chulett]

Warning, this is all IMHO:

It's a *surrogate key*, meaning in-and-of itself it has no value. I'm not sure why you would feel the need to reorder all of them to coincide with the date. Unless you are assigning significance to the key and assuming you can order by it to get date order, then it doesn't really matter if the 'older' dates have a 'higher' surrogate key value.

-craig

[ray.wurlod]

Craig is correct.
Equally, negative integers provide just as good uniqueness as positive integers. So, if you want to use negative integers, by all means do so.


Ray Wurlod
Education and Consulting Services
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