Re: No exceptions?
From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Sat, 01 Jul 2006 19:24:43 +0200
Message-ID: <e86b8l$i3l$1_at_orkan.itea.ntnu.no>
>
> I respectfully suggest the confusion caused by your use of key without
> the 'candidate' qualification demonstrates exactly why we have the term.
> I suppose irreducible key would do just as well, but for historical
> reasons, candidate key already means an irreducible key.
Date: Sat, 01 Jul 2006 19:24:43 +0200
Message-ID: <e86b8l$i3l$1_at_orkan.itea.ntnu.no>
Bob Badour wrote:
> Jon Heggland wrote:
>> "Every attribute" would also be a superkey (speaking loosely). The empty >> set is a subset of every set.
>
> I respectfully suggest the confusion caused by your use of key without
> the 'candidate' qualification demonstrates exactly why we have the term.
> I suppose irreducible key would do just as well, but for historical
> reasons, candidate key already means an irreducible key.
I don't think the confusion is on my part. "Key" (as opposed to "superkey") already implies irreducibility; that's the point of the superkey/key distinction. A "candidate key" is certainly irreducible (due to being a key), but "irreducible key" is redundant.
-- JonReceived on Sat Jul 01 2006 - 19:24:43 CEST