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Re: foreign key constraint versus referential integrity constraint

From: Marshall <marshall.spight_at_gmail.com>
Date: Sun, 25 Oct 2009 15:09:53 -0700 (PDT)
Message-ID: <928903b6-46b3-4a51-ae85-efe31e8f6232_at_v15g2000prn.googlegroups.com> 






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.



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!




Marshall



(Still hot; still grumpy.)
Received on Sun Oct 25 2009 - 23:09:53 CET












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