Oracle（00）：sum count null 结果

select sum(aa),sum(bb),count(bb),count(*),sum(aa+bb),sum(aa)+sum(bb) from

(select 1 aa,null bb from dual union all select 2 aa,1 bb from dual) tt

结果为：

SUM(AA)	SUM(BB)	COUNT(BB)	COUNT(*)	SUM(AA+BB)	SUM(AA)+SUM(BB)
3	1	1	2	3	4