update的有关问题

update的问题
update   a   set   a.ggxh=b.ggxh   where   a.wpbh=b.wpbh
该怎么写呢？

[解决办法]
update a set a.ggxh=b.ggxh from a,b where a.wpbh=b.wpbh
[解决办法]
update a set a.ggxh=b.ggxh From a,b where a.wpbh=b.wpbh

Or

update a set a.ggxh=b.ggxh From a inner join b on a.wpbh=b.wpbh
[解决办法]
update a set a.ggxh=b.ggxh
From a
inner join b on a.wpbh=b.wpbh

[解决办法]
update a set a.ggxh=b.ggxh from a,b where a.wpbh=b.wpbh