order by产生的 Using temporary的优化

今天遇到一个慢查询的sql，sql如下：

EXPLAIN
SELECT
	tas.f_year,
	tc.pk_id,
	tas.f_sex,
	tas.f_rank_score,
	tas.f_age,
	tas.f_km_five,
	tas.f_km_ten,
	tas.f_km_fifteen,
	tas.f_km_twenty,
	tas.f_km_halfway,
	tas.f_km_twentyfive,
	tas.f_km_thirty,
	tas.f_km_thirtyfive,
	tas.f_km_forty,
	tas.f_km_whole,
	tas.f_km_fifty,
	tas.f_km_hundred,
	tc.f_certifie_flag,
	tc.f_name AS tcf_name,
	tas.f_project,
	tas.f_finished_time,
	tas.f_good_score,
	tcs.f_begin_date
FROM
	mls.t_athlete_score AS tas
LEFT JOIN mls.t_comp_section AS tcs ON tas.fk_compsection_id = tcs.pk_id
LEFT JOIN mls.t_competition AS tc ON tas.fk_comp_id = tc.pk_id
WHERE
	tas.f_name = 'XXX'
AND upper(tas.f_card_num) = 'XXXX'
ORDER BY tcs.f_begin_date DESC

因为t_athlete_score 是主表，左连接到t_comp_section ，现在排序使用的第二个表的数据，所以产生了Using temporary，具体的产生原因，在
http://mysql.taobao.org/monthly/2015/03/04/
上讲的很清楚了，所以order by 产生Using temporary时，需要用主表的字段进行排序更合适一些，如果实在没有合适字段，再退而求其次。

EXPLAIN
SELECT
	tas.f_year,
	tc.pk_id,
	tas.f_sex,
	tas.f_rank_score,
	tas.f_age,
	tas.f_km_five,
	tas.f_km_ten,
	tas.f_km_fifteen,
	tas.f_km_twenty,
	tas.f_km_halfway,
	tas.f_km_twentyfive,
	tas.f_km_thirty,
	tas.f_km_thirtyfive,
	tas.f_km_forty,
	tas.f_km_whole,
	tas.f_km_fifty,
	tas.f_km_hundred,
	tc.f_certifie_flag,
	tc.f_name AS tcf_name,
	tas.f_project,
	tas.f_finished_time,
	tas.f_good_score,
	tcs.f_begin_date
FROM
	mls.t_athlete_score AS tas
LEFT JOIN mls.t_comp_section AS tcs ON tas.fk_compsection_id = tcs.pk_id
LEFT JOIN mls.t_competition AS tc ON tas.fk_comp_id = tc.pk_id
WHERE
	tas.f_name = 'XXX'
AND upper(tas.f_card_num) = 'XXXX'
#ORDER BY tcs.f_begin_date DESC
ORDER BY tas.f_date DESC;