From: Reindl Harald
Date: October 24 2011 4:32pm
Subject: Re: large temp files created by mysql
List-Archive: http://lists.mysql.com/mysql/226170
Message-Id: <4EA59329.6000603@thelounge.net>
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Am 24.10.2011 18:02, schrieb mos:
> At 10:34 AM 10/24/2011, you wrote:
>> select id from table order by rand() limit 1;
>> is doing as example a dumb temporary table with the full size
>=20
> Because it has to sort the entire table, then it returns the one row. T=
his of course is extremely inefficient. :)
> You need to choose a random row by using an auto-inc field. Something l=
ike:
>=20
> select id from table where id>=3Dmyrandomnum limit 1

but this is TOTALLY braindead if "id" is a primary-KEY with auto-incremen=
t


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