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From:Moon's Father Date:May 31 2009 8:38am
Subject:Re: Should I be able to DELETE FROM ... WHERE .. IN ( ... ) with
multiple a column key?
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As I know, IN sometimes invoke unmormal index.

On Thu, May 28, 2009 at 1:15 AM, Baron Schwartz <baron@stripped> wrote:

> Simon,
>
> On Wed, May 27, 2009 at 11:23 AM, Simon J Mudd <sjmudd@stripped> wrote:
> > perrin@stripped (Perrin Harkins) writes:
> >
> >> On Wed, May 27, 2009 at 6:43 AM, Simon J Mudd <sjmudd@stripped>
> wrote:
> >> > So is the format of the DELETE FROM .. WHERE ... IN ( ... )  clause I
> >> > propose valid and SHOULD the optimiser recognise this and be expected
> >> > to just find the 2 rows by searching on the primary key?
> >>
> >> Not according to the docs:
> >>
> http://dev.mysql.com/doc/refman/5.1/en/comparison-operators.html#function_in
> >
> > I'm not sure that the reference makes anything clear. The statements
> > are wrote ARE valid SQL and even though containing mulitiple column
> > values ARE "constants".
> >
> > Problem is I'm finding it hard to find a definitive reference to
> something
> > like this. I'll have to check my Joe Celko books to see if he mentions
> ths.
>
> Nothing's wrong with the SQL -- it's just that MySQL doesn't optimize
> this type of query well.
>
> See
> http://code.openark.org/blog/mysql/mysql-not-being-able-to-utilize-a-compound-index
>
> Regards
> Baron
>
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-- 
David Yeung,
MySQL Senior Support Engineer,
Sun Gold Partner.
My Blog:http://yueliangdao0608.cublog.cn
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Thread
Should I be able to DELETE FROM ... WHERE .. IN ( ... ) with multiple a column key?Simon J Mudd27 May
  • Re: Should I be able to DELETE FROM ... WHERE .. IN ( ... ) with multiple a column key?Perrin Harkins27 May
    • Re: Should I be able to DELETE FROM ... WHERE .. IN ( ... ) with multiple a column key?Simon J Mudd27 May
      • Re: Should I be able to DELETE FROM ... WHERE .. IN ( ... ) with multiple a column key?Baron Schwartz27 May
        • Re: Should I be able to DELETE FROM ... WHERE .. IN ( ... ) with multiple a column key?Moon's Father31 May