oracle sum求和的区别
不多说,看两个语句说说区别
语句一:
select sum(A.a),sum(B.b) from A, B where A.key=B.key
select c.suma, d.sumb from
(select A.key as key,sum(A.a) as suma from A group by A.key) C,
(select B.key as key,sum(B.b) as sumb from B group by B.key) D
where c.key=d.key
请问这两个求和语句的结果一样吗,据图区别是啥呢