原文链接：http://www.cnblogs.com/onesmail/p/6148979.html
方法一：
select distinct A.ID from A where A.ID not in (select ID from B)
方法二：
select A.ID from A left join B on A.ID=B.ID where B.ID is null
方法三：
select * from B where (select count(1) as num from A where A.ID = B.ID) = 0
方法四：
SELECT * FROM b WHERE NOT EXISTS(SELECT 1 FROM a WHERE tel_no=b.tel_no)
方法五：
--相同数据
select tel_no
from a
intersect
select tel_no
from b --不同数据
select tel_no
from b
except
select tel_no
from a