Re: MYSQL optimizer: Handling Subqueires
Posted by:
Rick James
Date: August 18, 2009 06:38PM
I believe the optimizer actually executes the subquery (after optimizing it) before optimizing the outer query. I once saw a query that took 13 hours to EXPLAIN. I tried the inner query manully; it took 13 hours to run, so I jumped to a conclusion.
It is usually more optimal to turn subqueries into JOINs.
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