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how to optimize this query
Posted by: Adrian Nye
Date: March 12, 2009 10:15PM

I have a table with pk, species, date in each row (plus other columns).
I want to select the one row for each species that has the most recent date. Currently I have the following which works slowly:

SELECT, f.species_name, from (select species_name, max(date) as maxdate from lister_importedsighting WHERE user_id=%s GROUP BY species_name)
as x inner join lister_importedsighting as f on f.species_name = x.species_name and = x.maxdate

With 30k rows, this takes 47 seconds which is way too long (it's a web application).
By the way MySQL 5.1.

One more thing, I need to be able to add up to three other columns to the inner where clause (applied before the maxdate is calculated).

What can I do to optimize this?


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how to optimize this query
March 12, 2009 10:15PM
June 12, 2009 06:25AM

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