Re: No exceptions?
From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 30 Jun 2006 05:49:59 GMT
Message-ID: <bY2pg.109995$Mn5.101623_at_pd7tw3no>
> All the attributes in a relation comprise, at least, a superkey. The
> set of attributes that qualify as a candidate key must hold unique
> values and no subset of those attributes must hold unique values. The
> only relations that could have empty candidate keys are those with
> empty headings, right?
Date: Fri, 30 Jun 2006 05:49:59 GMT
Message-ID: <bY2pg.109995$Mn5.101623_at_pd7tw3no>
>...
> All the attributes in a relation comprise, at least, a superkey. The
> set of attributes that qualify as a candidate key must hold unique
> values and no subset of those attributes must hold unique values. The
> only relations that could have empty candidate keys are those with
> empty headings, right?