mysql中join on的区别

我们有这两张表

image
我们先用查询
select A.ID as AID, B.ID as BID
from A left join B
on A.ID = B.ID
and B.ID<3
查询结果为:
image
再用
select A.ID as AID, B.ID as BID
from B left join A
on A.ID = B.ID
and B.ID<3;
image.png
把B表里的id<3的查出来了,还有A表里的其他数据