Re: Question about modeling
From: DA Morgan <damorgan_at_x.washington.edu>
Date: Wed, 26 Jan 2005 09:18:08 -0800
Message-ID: <1106759733.295242_at_yasure>
>
>
> <snip a detailed example, btw thanks>
>
>
> Hi Dan,
>
> Thanks for your detailed explanation, it seem that it is what I was
> looking for. I prefer to enforce referential integrity rules than to use
> constraint, it seem more efficient to me, or a least less error prone.
>
> You mention that there was a more efficient way to model it. Can I ask
> what is it ?
>
> Again, thanks for youre answer. It really do help.
>
> Mathieu Pagé
Date: Wed, 26 Jan 2005 09:18:08 -0800
Message-ID: <1106759733.295242_at_yasure>
Mathieu Pagé wrote:
> guntermann_at_verizon.net a écrit :
>
>> The constraint you mention can be structurally enforced with the use of >> superkeys as alternative keys. >> >> The following is a possibility in abbreviated notation. There is >> another, possibly more efficient way to model it as well, but I'll >> forego that for now. I am also explicitly not addressing referential >> integrity rules (ON UPDATE, DELETE, etc.). >> >> Let me know if you need clarification. >> CLIENTS(cl_id PK); >> >> DEPTS(d_id PK, cl_id FK references CLIENTS, AK (d_id, cl_Id)); >> >> CONTRACTS(cn_id PK, cl_id FK references CLIENTS, AK(cn_id, cl_id)); >> >> DEPTS_CONTRACTS(d_id, cn_id, cl_id, PK (d_pd, cn_id), FK (d_id, cl_id) >> REFERENCES DEPTS, FK (cn_id, cl_id) REFERENCES CONTRACTS)); >> >> ** Example Implementation Follows**
>
>
> <snip a detailed example, btw thanks>
>
>> >> HTH, >> >> - Dan >>
>
> Hi Dan,
>
> Thanks for your detailed explanation, it seem that it is what I was
> looking for. I prefer to enforce referential integrity rules than to use
> constraint, it seem more efficient to me, or a least less error prone.
>
> You mention that there was a more efficient way to model it. Can I ask
> what is it ?
>
> Again, thanks for youre answer. It really do help.
>
> Mathieu Pagé
You can but since you snipped the example I'm not sure what the original suggestion was I made. If you contact me off-line at the email address below I'll do so.
-- Daniel A. Morgan University of Washington damorgan_at_x.washington.edu (replace 'x' with 'u' to respond)Received on Wed Jan 26 2005 - 18:18:08 CET