Re: Deadly sins againts database performance/scalability

"Cris Carampa" <cris119_at_operamail.com> a écrit dans le message news: bq71jp$sq1$1_at_panco.nettuno.it...
> Marc Blum wrote:
>
> > (1)
> > SELECT DISTINCT ...
>
> Sorry for the naive question: what's wrong with SELECT DISTINCT?
>
> Kind regards,
>
> --
> Cris Carampa (spamto:cris119_at_operamail.com)
>
> "Poveri fanatici comunisti, noglobal e affetti dalla sindrome
> anti-microsoft" (gli utenti Linux secondo un poster di ICOD)
>

Most of the time, people use SELECT DISTINCT to get unique rows because they don't want to "bother" with the datamodel. They are lazy or hurried so they don't care about possible
keys, about WHERE clauses selectivity and all that kind of things so quick and dirty solution to be sure to get unique rows : SELECT DISTINCT which implies a sort therefore more activity to get the same result as they may have gotten quicker with a little bit work on the WHERE clause.

Alkos Received on Fri Nov 28 2003 - 03:43:29 CST