Oracle 将一个表中的字段值更新到另一个表的字段中

--使用where exists,则当数据存在时才会更新
update  sysrole role set system_name = (select system_name from temp_sysrole temp where role.rolename=temp.rolename)
where exists
(select system_name from temp_sysrole temp where role.rolename=temp.rolename);