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Re: Queries using JOIN and ORDER BY LIMIT
Posted by: Rick James
Date: March 13, 2012 11:07PM

> I am trying to optimize a query that joins 2 tables, using a column in one table to filter the data, and using a column in the other table to sort and limit the results.

Classis performance problem.

> limit 20 offset 20;

Smells like "pagination" done in the classic inefficient way. Instead, remember where you "left off". (We can discuss that if you like.)

> in ( select ...

Notoroiusly inefficient -- Unless the select greatly diminishes the number of rows (via GROUP BY, LIMIT, etc)

Are you thrashing the disk? Check the tunables:
http://mysql.rjweb.org/doc.php/memory

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Re: Queries using JOIN and ORDER BY LIMIT
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