"Brian Dick" <bdick_at_cox.net> wrote in message
news:jdtzxo8yz9ui$.fvz7df6zphej$.dlg_at_40tude.net...
> On 29 Sep 2004 10:21:38 -0700, Tony Andrews wrote:
>
>> Brian Dick wrote:
>>> On 28 Sep 2004 08:11:44 -0700, Tony Andrews wrote:
>>>> Of course, having the CID in the A table is a viable work-around,
>> but
>>>> that doesn't mean there was a relational design flaw before.
>>>
>>> You need to brush up on your normalization rules. Rule 3 states that
>>> columns must be dependent on nothing but the key. Your ATXT column is
>> not
>>> solely dependent on AID, so your design is not normalized.
>>
>> Wrong. ATXT is solely dependent on AID, it cannot be determined from
>> CID. But there is an additional constraint that ATXT must be unique
>> w.r.t. the CID for some reason. If you still think I'm wrong, then
>> please show the NORMALIZED database design that resolves the issue.
>> Not that it was MY column or design anyway!
>
> Mark C. Stock gave you a possibility. Although, his model implies that A
> is
> dependent on B is dependent on C. Is A.BID or B.CID nullable? If so, then
> Mark's model is not correct either. Need more info about the problem.
>
After some consideration (and a beer) I like the following better. If I had
a chance to study the business domain, I would probably come up with
something different, yet.
Table A(AID, BID ref. B.BID, TID ref T.TID)
Table B(BID, CID ref. C.CID)
Table C(CID)
Table T(TID, CID ref C.CID, ATXT) with unique constraint on CID, ATXT
Received on Wed Sep 29 2004 - 21:03:30 CDT
