(select num from t1 where...) - (select num from t2 where...)
这个只能取出结果的
但是select的时候我该怎么写呢？ 又必须写个from的嘛
------解决方案--------------------
没明白楼主啥意思
select col from(
(select num from t1 where...) - (select num from t2 where...)col
)
------解决方案--------------------
select
(select num from t1 where...) - (select num from t2 where...) a
from dual