Re: foreign key constraint versus referential integrity constraint
Date: Sun, 25 Oct 2009 20:15:22 -0300
Message-ID: <4ae4dc0d$0$23784$9a566e8b_at_news.aliant.net>
Marshall wrote:
> On Oct 24, 12:13 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
>>Domains, however, define what is or is not joinable because natural join
>>applies the equality comparison to attributes with like names, and
>>domains define equality comparisons.
>
> That may be the most practical perspective, but from a theoretical
> perspective, I find myself lately thinking that every value of every
> domain is theoretically able to be compared for equality with
> every value of every domain. If we are considering comparing
> an integer and a string, we can say with confidence ahead of
> time that the comparison will return that they are unequal.
(id in ??,name in string,contents in string) | }
> I also am suspicious of the idea of allowing a domain designer
> to define equality. From a theoretical standpoint, the system
> ought to know enough to figure it out, and from a practical
> standpoint, I've seen enough class designers screw it up
> with subtle and annoying consequences. Damn them!
I suppose in TTM, equality is implicit based on type and any arbitrary possrep.
> Marshall
>
> (Still hot; still grumpy.)
Yeah, it was hot here today to. It got all the way up into the 50's F. But to be fair, there was a nice gusty wind to take the edge off the heat. ;) Received on Mon Oct 26 2009 - 00:15:22 CET