mysql 执行 效率问题

这是第一条sql语句，执行时间 5s左右
select
...
from
`user` u,
(select u.id_card from user u left join purchase pe on u.user_id = p.user_id
where pe.purchase_status_id = 4 group by u.id_card having count(pe.purchase_id) = 1) a,
purchase pe, product pt
where
u.id_card = a.id_card and u.user_id = p.user_id and p.product_id = pt.product_id and
p.purchase_status_id = 4 and pt.fake_repayment_time < date_sub(current_date, interval 1 month)
group by u.id_card
order by 5;

第二条sql语句，执行时间10s左右
select
...
from
(select u.user_id, u.authentic_name, u.phone_number, u.id_card,
pe.purchase_begin_time, pt.`name`, pt.fake_repayment_time
from user u, purchase pe, product pt
where u.user_id = pe.user_id and pe.product_id = pt.product_id and pe.purchase_status_id = 4
group by u.id_card having count(pe.purchase_id) = 1) t
where t.fake_repayment_time < date_sub(current_date, interval 1 month)
order by 5;

我的直观感觉应该是第一条sql执行更慢，但实际是第二条执行慢，请问原因是什么。
代码不方便观看的话，用美化器美化下把。

如果是相同条件下，当然是第一条了，第二天又相当于创建了一个临时表！
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不是innodb执行插入操作比myisam高效，而是说innodb支持回滚等事务处理，当有多并发操作时可以保证事务安全，插入速度还是myisam比较快的