how to combine three sql selects into one query

Question

I have the three queries below, I would like to combine them into one query so I get three columns with results by county. I tried doing an inner join with all of the tables, b

Answer 1

One way to do it would be to convert your existing queries into inline tables like this - you don't need the select from Counties table as you've already got that table in your first two queries:

select co.Description, a.[Total DLL Children], b.[Total Children]
from
(select co.id,[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.id, co.Description) a
 join 
 (select co.id, co.Description, [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.id, co.Description) b on a.id = b.id

Answer 2

Please try this. Basically, each subquery, you need to return County.Description too, then you can join them together.

 SELECT A.Description, B.[Total DLL Children], C.[Total Children]
 FROM (
     select co.Description from Counties as co
     group by co.Description
     ) A
 LEFT JOIN 
     (
         select co.Description, [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
      ) B
      ON A.DESCRIPTION = B.DESCRIPTION 
LEFT JOIN 
      (
         select co.Description, [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
      ) C
      ON A.DESCRIPTION = C.DESCRIPTION