/*
两个表结构一样，
Id    int    
LoginName    varchar(50)    
num    int    
Grade    int    

数据如下：
t1
1    zhangsan    1    1
2    lisi    4    1
3    wangwu    7    4
4    xiaoming    3    3


t2
1    zhangsan    8    1
2    lisi    9    1
3    wangwu    8    4
4    xiaoming    8    3

怎么可以查询成下面的结果
根据去除重复的loginname获取sum(num)
1 zhangsan 9  1
2 lisi    13 1
3 wangwu 15 4
4 xiaoming 11 3



*/

select a.id,a.loginname,a.num+b.num as num a.grade
from t1 a inner join t2 b on a.id=b.id

------解决方案--------------------
SELECT ID,LOGINNAME,SUM(NUM),GRADE
FROM
(SELECT * FROM A
UNION ALL  
SELECT * FROM B)
T  
GROUP BY ID,LOGINNAME,GRADE


------解决方案--------------------
SQL code
select LoginName,sum(num) from
(select LoginName,num from A union all select LoginName,num from B)t
group by LoginName

------解决方案--------------------
SQL code
select
 LoginName,sum(num) 
from
(select LoginName,num from A union all select LoginName,num from B)t
group by
 LoginName