Re: WWW/Internet 2009: 2nd CFP until 21 September x

From: paul c <toledobythesea_at_oohay.ac>
Date: Sun, 16 Aug 2009 20:00:11 GMT
Message-ID: <fzZhm.39346$Db2.21087_at_edtnps83>



Walter Mitty wrote:
...
> When you have ot produce reports, outer joins can be useful. Trust me.
>
> The fact that an outer join on two relations does not yield a relation
> should be a clue to those who want to work out the operation of a database
> engine in terms of mathematics. To those of us who are simply using tools
> like SQL to build systems, the mathematics sometimes helps and sometimes
> doesn't.
>
> Having said that, I agree with those who say that the reason relational
> databases have endured so long and worked so well is that they are more
> nearly grounded in sound mathematics than most of the stuff in computer
> science.

I'll have to ponder that. I wouldn't argue against a report table representing multiple relations and therefore multiple predicates, but I'm still not very comfortable with understand how group, group by, and aggregate definitions fit together. Received on Sun Aug 16 2009 - 15:00:11 CDT

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