Question

I have three MySQL queries I need to combine into a single query using joins. I’m having a lot of trouble figuring out how to do it though. Here are the three queries.

select 
    sum(A.a) 
from A join B 
on A.BID = B.id 
where B.userID=userID

select 
    sum(C.c)
from D left join (C) 
on (D.id=C.DID)
 where D.userID = userID

select sum(E.e) from E where E.userID=userID

I need to somehow combine all of these queries into a single query joined with the user table to give me sum(A.a)+sum(C.C)+sum(E.e) for each user.id. I tried a left join across all tables

user left join (A, B, C, D, E)
on ((A.BID = B.id and B.userID=user.id) 
    or (D.id=C.DID and D.userID = user.id) 
    or (E.userID=user.id))

It was pretty much a shot in the dark and it failed spectacularly. I have no idea how to combine these three queries, anyone give me a hint?

Edit to clarify: I need this query to be a join of the user table with the above queries, because I need to be able to select all user ids ordered by the sum_value. The three previous queries were run individually and parameterized with a single userID.

Futher edit: Tried every variation of union all joined to the user query I could think it, it doesn’t work. It comes very close to working with some tweaking, but it still returns incorrect values. I’m not really sure why it is doing that.

Answer 1

select 
   ( ( select 
        sum(A.a)
    from 
        A join B 
        on A.BID = B.id 
    where 
        B.userID = user.ID ) + 
    ( select 
          sum(C.c)
      from 
          D left join (C) 
          on (D.id = C.DID)
     where D.userID = user.ID ) +
    ( select
          sum(E.e)
      from 
          E 
      where 
          E.userID = user.ID ) )
from
    user