SELECTCOUNT(1)asnum,uid,sid,usernameFROMsd_usersGROUPBYsidHAVINGnum>1ORDERBYnumDESC在實際測試中發(fā)現(xiàn)由于數(shù)據(jù)量超過60萬在group的時候就產(chǎn)生了巨大的威脅力，查詢執(zhí)行緩慢一直停留在copytmptable下explain發(fā)現(xiàn)需要重建索引導(dǎo)致請問類似的語句應(yīng)該如何優(yōu)化+----+-------------+-----------+-------+---------------+-----+---------+------+--------+---------------------------------+|id|select_type|table|type|possible_keys|key|key_len|ref|rows|Extra|+----+-------------+-----------+-------+---------------+-----+---------+------+--------+---------------------------------+|1|SIMPLE|sd_users|index|NULL|sid|97|NULL|539029|Usingtemporary;Usingfilesort|+----+-------------+-----------+-------+---------------+-----+---------+------+--------+---------------------------------+1rowinset