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Re: [PROGRAMMERING] [SQL] group by hjælp



On Mon, 4 Jun 2007 20:49:55 +0000 (UTC)
Troels Arvin <sslug@sslug> wrote:

> Den Sat, 02 Jun 2007 23:09:14 +0200 skrev Kim Schulz:
> >> Og heller ikke i postgresql.. som sagt .. en bug i mysql.
> >> 
> >> 
> > NEJ! en alternativ implementation. Ifølge de seneste  SQL standarder
> > (både ISO og ANSI) er der ikke mere krav om at alle SELECT kolonner
> > er aggregerede
> 
> Jo, med mindre DBMSet implementerer den valgfri "functional
> dependencies" feature (T301). Og det kender jeg ikke til, at MySQL
> skulle implementere; i hvertfald kender jeg ikke til, at MySQL skulle
> tjekke funktionelle afhængigheder såfremt man undlader
> ikke-aggregerede elementer i sin SELECT-liste.
> 
> På http://rpbouman.blogspot.com/2007/05/debunking-group-by-myths.html
> kan man læse lidt om sagen. Men jeg synes, at nævnte artikel
> misbruger SQL:1999 (og senere)'s mulighed for mere "liberal" GROUP BY
> til at blåstemple MySQL's GROUP BY fortolkning, som jeg altså ikke
> finder gyldig.
> 

Jeg synes det er en fin artikel og jeg er umiddelbart enig i det meste
han skriver. Efter at have læst igennem SQL specs en del gange må jeg
indrømme at det på rigtigt mange områder giver fin anledning til
tvivl om hvad der er rigtigt og hvad der er forkert. Den er simpelthen
så tvetydig flere steder at det er galt. Men sådan er det jo desværre
med de fleste standarder. 


-- 
    Kim Schulz       | Blog: http://www.schulz.dk/
Email: sslug@sslug | Work: http://www.devteam.dk/
Phone: +45 5190 4262 | Fun : http://www.chilifan.dk/


 
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