Re: Many To Many Relationships
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 17 Apr 2007 12:02:05 GMT
Message-ID: <1H2Vh.25350$PV3.257239_at_ursa-nb00s0.nbnet.nb.ca>
>
> has
>
>
> is
>
>
> Then again, I'm thinking that maybe there is a lesson for theoreticians to
> learn in this exchange.
>
> Turning relational data into hierarchical data is "trivial", in every sense
> of the word. turning hierarchical data into relational data is, in some
> cases, non trivial. This suggests that storing database data in relational
> form is better than storing it in hierarchical form, provided there is some
> utility in doing so.
>
> Most theoreticians already know this, and know it better than I have
> verbalized it. But it's worth making it explicit.
Date: Tue, 17 Apr 2007 12:02:05 GMT
Message-ID: <1H2Vh.25350$PV3.257239_at_ursa-nb00s0.nbnet.nb.ca>
David Cressey wrote:
> "Marshall" <marshall.spight_at_gmail.com> wrote in message
> news:1176756330.363208.181810_at_o5g2000hsb.googlegroups.com...
>
>>On Apr 16, 1:20 pm, "David Cressey" <cresse..._at_verizon.net> wrote: >> >>>>Something like that. Requires RVAs and an aggregate union. >>>>Clearly no standard way to do in SQL, but there might be >>>>some hack that lets you do the union as a string operation >>>>which might be sufficient for some applications. >>> >>>OK, but what I offered was not a hack. For once, I was trying to give a >>>serious response to this kind of question. >>> >>>(You may not recognize it as such, but it's the same question that Dawn
>
> has
>
>>>raised a dozen times in the last few years.) >>> >>>Pushing the result of a SQL query through a hierarchical report writer
>
> is
>
>>>really not hacking. It's serious work, albeit without much theoretical >>>merit at all. >> >>Oh, totally. I didn't intend to detract from your answer at all. >>Your answer was practical; mine was almost entirely impractical.
>
> Then again, I'm thinking that maybe there is a lesson for theoreticians to
> learn in this exchange.
>
> Turning relational data into hierarchical data is "trivial", in every sense
> of the word. turning hierarchical data into relational data is, in some
> cases, non trivial. This suggests that storing database data in relational
> form is better than storing it in hierarchical form, provided there is some
> utility in doing so.
>
> Most theoreticians already know this, and know it better than I have
> verbalized it. But it's worth making it explicit.
Actually, expressing a hierarchy in relations is trivial too. In fact, expressing general graphs in relations is trivial. What's not trivial is expressing a general graph in a hierarchy. Received on Tue Apr 17 2007 - 14:02:05 CEST