Question

我在下面有两个以下的查询，Total回来了不同，但我在每个查询中以相同的方式添加总和。为什么总回来会有所不同？

    select [Total Children] = (SUM(demo.NumberOfPreschoolers) + SUM(demo.NumberOfToddlers) + SUM(demo.NumberOfInfants)),
County = co.Description
from ClassroomDemographics as demo
inner join Classrooms as c on demo.Classroom_Id = c.Id
inner join Sites as s on c.Site_Id = s.Id
inner join Profiles as p on s.Profile_Id = p.Id
inner join Dictionary.Counties as co on p.County_Id = co.Id
where co.Description = 'MyCounty'
Group By co.Description


select [Number Of DLL Children] = SUM(cd.NumberOfLanguageSpeakers),
[Total Children] = (SUM(demo.NumberOfPreschoolers) + SUM(demo.NumberOfToddlers) + SUM(demo.NumberOfInfants)),
County = co.Description
from ClassroomDLL as cd
inner join Classrooms as c on cd.Classroom_Id = c.Id
inner join Sites as s on c.Site_Id = s.Id
inner join Profiles as p on s.Profile_Id = p.Id
inner join Dictionary.Counties as co on p.County_Id = co.Id
inner join ClassroomDemographics as demo on c.Id = demo.Classroom_Id
where co.Description = 'MyCounty'
Group by co.Description

Answer 1

快速浏览一下这两个阙，我猜想：

inner join ClassroomDemographics as demo on c.Id = demo.Classroom_Id

第二个查询中的

排除了第一个查询中的结果，因此聚合值将不同。

Answer 2

您对Classrooms表的加入是在第二个查询中加入一个额外的表。

查询1：

from ClassroomDemographics as demo
inner join Classrooms as c on demo.Classroom_Id = c.Id

查询2：

from ClassroomDLL as cd
inner join Classrooms as c on cd.Classroom_Id = c.Id
...
inner join ClassroomDemographics as demo on c.Id = demo.Classroom_Id

我敢打赌，ClassroomDLL表中的数据较少，或者其中一个连接条件列的行为空，其中任何一行都可以从结果中排除行并关闭总计。

sql查询总和带回不同的结果

2 个答案: