三张表组合统计
有三张表：
表1：
TableName   :   A
Num       UserID
1             1
10           2
20           5

表2:
TalbeName   :   B
Num       UserID
5             1
14           5
8             7      

表3:
TableName   :   C
Num       UserID
5             1
14           9  

我想把这三张表组合起来生成D表
Num       UserID
11           1
10           2
34           5  
8             7
14           9


sql语句怎么写

------解决方案--------------------
select sum(num) as num,[UserID]
from
(
select * from A
union all
select * from B
union all
select * from C
) T
group by [UserID]
------解决方案--------------------
select Num , UserID from
(
select UserID , sum(Num) as Num from A group by UserID
union all
select UserID , sum(Num) as Num from B group by UserID
union all
select UserID , sum(Num) as Num from C group by UserID
) t
order by UserID