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Re: left outer join performance
Posted by: Rick James
Date: November 29, 2011 09:27PM

Learn about "compound indexes".

on a.Memberid_t = b.Memberid_DC
and a.YEAR_t = b.YEAR_dc;
begs for
INDEX(Memberid_t, YEAR_t) -- on table a
and/or
INDEX(Memberid_DC, YEAR_DC) -- on table b
In this case, the order of the fields in the compound index is not important.

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