2014/5/0 ????
select a.time,a.amt_a+b.amt_b from
(select trunc(date,'yyyy/mm') time,sum(amt) amt_a from A group by trunc(date,'yyyy/mm')) a,
(select trunc(date,'yyyy/mm') time,sum(amt) amt_b from B group by trunc(date,'yyyy/mm')) b where a.time=b.time
时间那块的截取要测一下，可能要稍微修改下
