标题：[分享][推荐]ORACLE的左连接left join 右连接right join 介绍及用法

(1)左连接 left join 在查询结果中包含join左侧表中的所有记录，以及join右侧表中匹配的纪录
(2)右连接 right join 在查询结果中包含join右侧表中的所有记录，以及join左侧表中匹配的纪录
(3)全连接 full join 在结果中包含join.

例子如下：

select
nvl(left_.dummy,'这是要右边的全部') left_dummy,
nvl(right_.dummy,'这是要左边的全部') right_dummy
from dual left_ left JOIN dual right_
on left_.dummy||'d' = right_.dummy

select
nvl(left_.dummy,'这是要右边的全部') left_dummy,
nvl(right_.dummy,'这是要左边的全部') right_dummy
from dual left_ RIGHT JOIN dual right_
on left_.dummy||'d' = right_.dummy

select
nvl(left_.dummy,'这是要右边的全部') left_dummy,
nvl(right_.dummy,'这是要左边的全部') right_dummy
from dual left_, dual right_
WHERE left_.dummy||'d' = right_.dummy(+)