oracle代替mysql limit的语句：
select * from
(select rownum r,t.* from
(select seckill_id, name, quantity, start_time, end_time, create_time
from seckill
order by create_time desc) t where rownum <![CDATA[<=]]> (#{offset}+#{limit}))
where r <![CDATA[>=]]> #{offset}
test前还在想这样会不会报错，结果发现这条可以用，哈。
