求一个简单的SQL语句，多主键查询的。。
t1表：
ip port
==================
A 1
A 2
B 1
B 2
t2表
ip port
==================
A 1
B 2
A 3
B 4
我要查询t1表中不在t2表中的记录，即要得到t1表中的：
A 2
B 1
这两条记录，请问应该怎么操作？
[解决办法]
select *
from t1
where ip & port not in (select ip & port from t2)
--或
select a.*
from t1 as a
left join t2 as b on a.ip=b.ip and a.port = b.port
where isnull(b.ip) or isnull(b.port)
