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Re: query performance optimization
Posted by: Øystein Grøvlen
Date: January 19, 2016 02:30AM


I am not able to understand what your query is supposed to do. The GROUP BY clause puzzles me:

GROUP BY SFO.entity_id AND SOIT.id_tags IN (2,3,8,10,11,12)

Grouping on a logical expression means you will get two groups, one for the rows where the expression is TRUE and one for rows where the expression is FALSE (and maybe an additional NULL group if SOIT.id_tags happens to be NULL for some rows.) This does not make much sense since you will just get data from some arbitrary row within each group. In this context, LIMIT 5 does not make much sense either since there will never be more than 3 rows in the result.

Which version of MySQL are you using?

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway

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Written By
January 18, 2016 04:49AM
Re: query performance optimization
January 19, 2016 02:30AM
January 22, 2016 06:29PM
January 22, 2016 01:08PM
January 22, 2016 11:10PM

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