WOW!
Jan-Erik Rosinowski wrote:
> >if a column is declared as a unique key it will allow null
> >value in that column (but only once) since the column is unique and
> >therefore null values can occur but only once
>
> from my point of understanding 'null' is similar to infinity in
> mathematics. nothing can be equal to infty. for that very reason null
> IS null but (null=null) IS null..
>
> so i don't understand how null can be really unique or why on the
> other hand, null isn't allowed in a pk (w/ the same semantics)
>
> anybody any further insights?
>
> ciao, jan
>
> http://www.rsp.de - Software zur effizienten Erstellung und Verwaltung von
> Gutachten, Analysen, Pruefprotokollen etc.
Received on Mon Jan 24 2000 - 09:45:19 CST
