You asked this earlier this week.
The answer has not changed.
Matt Heaton wrote:
> Hi all, trying to do something and have it be as efficient as possilble. My
> question is if I have a table with say 10,000 rows in it, and I issue
> a command like this
>
> select * from table where number=1 order by rand() limit 1;
>
> If 1000 rows would match this command does mysql first find all 1000 rows
> and THEN randomly select 1 of those to return, OR does it just randomly
> start somewhere and then stop when it finds one? The first method would
> be really slow and inefficient, but I am afraid that is how it works? Is
> there anyone out there that knows FOR SURE how the order by rand() operation
> works? I can't find a specification out there for it.
>
> Thanks,
> Matt Heaton
>
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--
Gerald L. Clark
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