http://nippondanji.blogspot.jp/2009/03/using-filesort.html
select * from users where rid = 3 order by unm;
alter table users add index idx_rid_unm (rid, unm);
Using Where が Using index condition に
http://nippondanji.blogspot.jp/2009/03/using-filesort.html
select * from users where rid = 3 order by unm;
alter table users add index idx_rid_unm (rid, unm);
Using Where が Using index condition に