Re: 1NF (Marshall)
Date: Mon, 22 Jan 2007 22:59:33 GMT
Message-ID: <plbth.789582$R63.681002_at_pd7urf1no>
DBMS_Plumber wrote:
> paul c wrote:
>
>
>>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#.
>
>
> I agree.
>
> In the first place, the "unnesting" here loses information;
> specifically, how many of each part was shipped. That might be OK for
> the purposes of defining the operation but I observe that it will
> significantly complicate data modeling.
> ...
Not being very hip to all the data modelling tasks I've seen people spending time at, whether they are important or spurious, I can't guess exactly what this means, but I do think a requirement of storing all combinations of parts shipped to any customer will complicate somebody's life, just like most requirements will do.
I was more trying to point out that in this case, unnest becomes an operator that makes an inference, overlapping with projection if you will, whereas what little I've read about unnest suggested to me that it was intended as a mere technical device to eliminate rva's for some purpose external to the rdbms, such as providing a clearer user interface or exporting to an array.
p Received on Mon Jan 22 2007 - 23:59:33 CET