select userid from test1,test2 where test1.userid=1 or test2.userid=2
select userid from test1,test2 where test1.userid=1 or test2.userid=2 and userid not in (select userid from test1,test2 where test1.userid=1 and test2.userid=2) 也就是两个表的"或"关系减去两个表的"与"关系的结果
我用个最 直观的,但不对的语句八 select test1 as userid=111 union all 并且 select test2 as userid=111具体怎么做!?
select * from test1 where userid=1 union all select * from test2 where userid=2
谢谢,对了。select userid from test1,test2 where test1.userid=1 or test2.userid=2 用这个,是我下面的判断出错
但那个或者怎么加入进去!?
如果表一中有userid=1或者表二中有userid=22
那么执行后面语句
两个表中都有用户字段。为userid现在要找出 只要有一个表中有userid=某某,就执行下面语句。其中两个表的关系是或者,不是同时
(select userid from test1,test2 where test1.userid=1 and test2.userid=2)
也就是两个表的"或"关系减去两个表的"与"关系的结果
select test1 as userid=111 union all 并且 select test2 as userid=111具体怎么做!?
用这个,是我下面的判断出错