A.
select count(*) as num ,
case when groupping(deptno)=1 then '合计' else
deptno end as dd
from scott.deptno
group byrollup(deptno)
B.
select count(*) as num ,deptno from scott.emp group by deptno
union all
select sum(num),'合计' from
(
select count(*) as num ,deptno from scott.emp group by deptno)