Re: Differentiate between candidate key and super key

"Low Yew Sing" <slasher_at_singnet.com.sg> wrote in message news:89m0im$hu7$1_at_violet.singnet.com.sg...

> How to differentiate between a candidate key and a super key? i can;t
> understand what my txtbk is trying to say? Anybody can help?
> If possible, quote examples.

Doesn't a superkey have unnecessary junk in addition to what's needed to uniquely identify a record? If a person can be uniquely identified by either the full name or a taxpayer ID number, both are candidate keys. Combining the name and, say, the gender would be a superkey, since the person can be identified by the name alone.

--
Joe Foster <mailto:jfoster_at_ricochet.net>  Space Cooties! <http://www.xenu.net/>
WARNING: I cannot be held responsible for the above        They're   coming  to
because  my cats have  apparently  learned to type.        take me away, ha ha!