Sql 试图计算重量之和

我返回四列多行值 并且需要其中一个列值的聚合

我返回四列多行值 列：weight，a，b，c，d它包含18行值，现在我想从中得到一列weight的聚合，即sum（weight）

预期值：权重列中所有值的总和。 实际值：仅获取列中的权重值如何从两个表联合的结果中进行聚合不知道。

您可以在下面进行尝试-

select sum(weight) as totalweight
from
(
select  a.prod_weight as weight,a,b,c,d from tbl1
union all
select  a.prod_weight,a,b,c,d from tbl2
)A 

你可以试试这个

Select sum(isnull(weight,0)) as Weight, a, b, c, d from (
select  a.prod_weight weight, a, b, c, d from tbl1
union all
select  a.prod_weight weight, a, b, c, d from tbl2
) as d 
group by a, b, c, d

或者，如果只想在最后一列中添加sum，则不需要列：-

select  a.prod_weight weight,a,b,c,d from tbl1
union all
select  a.prod_weight weight,a,b,c,d from tbl2
union all
Select sum(isnull(weight,0)) as Weight, null, null, null, null from (
select  a.prod_weight weight,a,b,c,d from tbl1
union all
select  a.prod_weight weight,a,b,c,d from tbl2
) as d 

---

我猜您希望在这里使用UNION ALL而不是UNION。查询很好，但我只需要单列totalweight，它将weight列中每行值的总和作为单个TotalWeights。除非您希望产生删除重复项的开销，否则不要使用

UNION

。如果两个表具有相同的值，则将返回不正确的结果。

select  a.prod_weight weight,a,b,c,d from tbl1
union all
select  a.prod_weight weight,a,b,c,d from tbl2
union all
Select sum(isnull(weight,0)) as Weight, null, null, null, null from (
select  a.prod_weight weight,a,b,c,d from tbl1
union all
select  a.prod_weight weight,a,b,c,d from tbl2
) as d