select owner, object_type, count(*)
from dba_objects
group by owner, rollup(object_type)
rollup有合计的作用
select sum(column) from table1
sum()函数 合计列值
你说的是聚合函数把,之前下过一个总结的不错的,还有一些别的函数的总结
http://www.itpub.net/forum.php?mod=viewthread&tid=843333&extra=page%3D1%26filter%3Ddigest%26digest%3D1%26digest%3D1
百度知道