Re: Design question : Nullable FK & FK To Unique Key

Hi,

>1. Generally the same as having index on nullable columns.
This is FTS issue right ? I try not use two different tables because all other attributes is the same except for this nullable column, what is other solution to this condition ?

> 2. Why? Why do you use unique constraint in place of PK?
Because I use Surrogate Key as PK and natural Key as Unique constraint, and when doing data entry user is using natural Key.

Thank you,
xtanto

On Nov 9, 8:34 pm, afatku..._at_gmail.com wrote:
> """krisl..._at_gmail.com ΠΙΣΑΜ(Α):
> """
>
> > Hi gurus,
>
> > Our Invoice may or may not has Orders before it. User can input order
> > and produce invoice from it, OR they can just input Invoice without
> > order. So we plan to have Nullable FK on Invoice.
>
> > The question is :
>
> > 1) What is the bad side of Nullable FK ?
>
> > 2) FK from Invoice to Orders , not refering to PK , but to the Unique
> > Key of the Orders, what is the bad side of this ?
>
> > Thank you for your help,
> > xtanto1. Generally the same as having index on nullable columns.
> 2. Why? Why do you use unique constraint in place of PK?
Received on Thu Nov 09 2006 - 08:01:43 CST