关于数据统计时的效率

如：
select t.sid,t.qymc,t1.dl_count,t2.qy_ybyh_count from
(
select sid,qymc from base_qyxx  
where (ISDELETED= 0 or ISDELETEDis null)
and ID = ‘000100090002‘
) t
left join
(
select userid,count(1) dl_count 
from sys_log_login l
where l.logindate >= to_date(‘20140501‘, ‘yyyyMMdd‘)
and l.logindate <= to_date(‘20140731‘, ‘yyyyMMdd‘)
group by userid
) t1
on t.sid=t1.userid
left join
(
select qyid,count(1) qy_ybyh_count
from hidden_danger_ybyhxx ybyh 
where (ISDELETEDis null or ISDELETED= 0)
and (zfjcid is null)
and ybyh.cjsj >= to_date(‘20140501‘, ‘yyyyMMdd‘)
and ybyh.cjsj <= to_date(‘20140731‘, ‘yyyyMMdd‘)
group by qyid
) t2
on t.sid = t2.qyid