Oracle 实现按周、月、季度、年查询统计数据

//按自然周统计 
select to_char(date,'iw'),sum() 
from 
where 
group by to_char(date,'iw') 

//按自然月统计 
select to_char(date,'mm'),sum() 
from 
where 
group by to_char(date,'mm') 

//按季统计 
select to_char(date,'q'),sum() 
from 
where 
group by to_char(date,'q') 

//按年统计 
select to_char(date,'yyyy'),sum() 
from 
where 

group by to_char(date,'yyyy')

出处：http://www.cnblogs.com/skl99/archive/2009/12/05/1617630.html