>Hi,
>I read couple of articles that talk about primary key, and it mentioned that we should use integer as primary key and don try to re-use it. If we need something unique such as ID number or customer code, we could place it as candicate key. It is the same effect.
>
>I am not very clear about:
>1. Since, filtered index is not optimize, how am I going to re-use the deleted candicate key but not effect the speed?

Your Candidate key can have a filter, and you can have another TAG on the same field but without the filter.


>
>2. If I have a auto-generated field like Invoice No., do yoo think it is good to be primary key or candicate key??

Sounds like a good choice.


>
>Thank you