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Re: Query with GROUP BY not using Index
Posted by: Rick James
Date: August 18, 2012 10:30PM

Can you use VARCHAR(255) instead of (256)? That would eliminate the need for "prefixing".

You really need
INDEX(wafer_name, date)

It does not make sense to GROUP BY one set of things, then ORDER BY something that is not in the GROUP BY list! Which `date` would be used for a given wafer_name??

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