SQL查詢總結帶來不同的結果

我有以下兩個查詢下面，總是回來不同的結果，但我在每個查詢以相同的方式添加總和。爲什麼總回來不同？SQL查詢總結帶來不同的結果

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

來源

2013-03-27 user1220099

請注意，第二個查詢有一個額外的內部聯接。兩個結果集中的行數是否相等？ – cdlong 2013-03-27 15:31:47

每個結果集中只有一行，第二個查詢有三列信息，第一個查詢只有兩列信息。額外的內部連接應該在第二個查詢中，因爲我需要額外的信息列。 – user1220099 2013-03-27 15:33:19

對不起，只是爲了澄清，你是否曾嘗試在兩個查詢上運行原始選擇（沒有聚合），並驗證結果集具有相同數量的記錄。基本上只是詢問@Brandon Moretz的回答如下。 – cdlong 2013-03-27 15:34:41

只是一個快速瀏覽一下這兩個querties中，我推測是：

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

中不計成績是在第一個查詢的第二個查詢，爲此彙總值會有所不同。

來源

2013-03-27 15:32:52

該連接在兩個查詢中（雖然在不同的地方，並且連接以相反的方式構建，所以難以比較兩者）。我認爲第二個查詢中'ClassroomDLL'的連接實際上是排除結果的連接。 – Stainy 2013-03-27 16:09:13

您加入到Classrooms表正與第二個查詢中的附加表連接。

查詢1：

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

問題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

我的賭注是，ClassroomDLL表中有較少的數據，或者具有帶有用於連接標準中的一個空行，其中任何一項都可以排除結果中的行並拋出您的總計總計。

來源

2013-03-27 15:44:12 Stainy

SQL查詢總結帶來不同的結果

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