Re: 1NF (Marshall)

Marshall wrote:
> ...
> It does seem to me, though, that despite any relaxing of 1NF,
> we can get ourselves in to trouble with too much nesting.
> However the reverse isn't true; there is no trouble associated
> with unnesting. At worst you are talking inconvenience.
> ...

I have a problem with unnesting of some relations. If I have relation that has the unique combinations of parts ever shipped to any customer, eg.,

S{{P#}} = {

            {p1,p2},
            {p1,p3}
           }

and I unnest it I get

SU{P#} = {

           p1,
           p2,
           p3
          }.

I would say SU doesn't mean the same thing as S. Maybe this isn't a problem to anybody else, but it troubles me if you are saying that the meaning can be preserved by unnesting alone, eg., without the introduction of other attribures than P#.

p Received on Sat Jan 20 2007 - 20:23:58 CET