Postgresql 连接更新

update dbo.m_role_fun a
set role_code = b.rsc
from (select rsc, fun_code from dbo.m_fun) b
where a.fun_code = b.fun_code

几个开源数据库的连接更新的写法都不同，比较下来还是Postgres优雅点。

回顾下MySQL写法：

update A 
join B on A.x = B.x
set A.xx = B.xx

Firebird 写法：

MERGE INTO  target [[AS]  target-alias ]
USING  source [[AS]  source-alias ]
ON  join-condition
WHEN MATCHED THEN UPDATE SET  colname =  value [,  colname =  value ...]
WHEN NOT MATCHED THEN INSERT [( <columns> )] VALUES ( <values> )