sql - sql查询组合

Question

我有下面的三个查询，我想将它们组合成一个查询，所以我得到三列按县列出的结果。我尝试对所有表进行内部连接，但我得到了错误的数据。如何结合这三个查询并按县分组？

select co.Description
from Counties as co
group by co.Description


select [Total DLL Children] = SUM(cd.NumberOfLanguageSpeakers)
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 Counties as co on p.County_Id = co.Id
group by co.Description


select
  [Total Children] = (SUM(demo.NumberOfPreschoolers)
     + SUM(demo.NumberOfToddlers) + SUM(demo.NumberOfInfants))
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 Counties as co on p.County_Id = co.Id
group By co.Description

Answer 1

你可以使用子查询来做到这一点

 select co.Description, demo.[Total Children], cd.[Total DLL Children]
 from Classrooms as c
 left outer join (select SUM(NumberOfPreschoolers) + SUM(NumberOfToddlers) + SUM(NumberOfInfants) as [Total Children], Classroom_id 
                    from ClassroomDemographics group by Classroom_id) as demo on demo.Classroom_id = c.Id
 left outer join (select SUM(NumberOfLanguageSpeakers) as [Total DLL Children], Classroom_id 
                    from ClassroomDLL group by Classroom_id) as cd 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 Counties as co on p.County_Id = co.Id
 group By co.Description