select a.somefield, b.someotherfield
from a, b
where a.key = b.key
以上是否等同于:
select a.somefield, b.someotherfield
from a join b on a.key = b.key
或者:
select a.somefield, b.someotherfield
from a full join b on a.key = b.key
我很确定它相当于一个内部连接,但只是意识到我以前从未真正考虑过它。另外我想知道是否有任何边缘情况不是100%等效的?