FULL OUTER JOIN with Subqueries

Question

I have a query which I am simplifying. The original structure of the query looks something like this:

SELECT one.*, two.*
FROM 
(
    SELECT *
    FROM dbo.TableA1 as A1 INNER JOIN dbo.TableB1 as B1 ON A1.ID = B1.ID
) as one
FULL OUTER JOIN
(
    SELECT *
    FROM dbo.TableA2 as A2 INNER JOIN dbo.TableB2 as B2 ON A2.ID = B2.ID
) as two
ON one.ID = two.ID and one.AnotherID = two.AnotherID

An optimised version (according to query execution plans) would be:

SELECT A1.*, A2.*
FROM 
    dbo.TableA1 as A1 INNER JOIN dbo.TableB1 as B1 ON A1.ID = B1.ID
FULL OUTER JOIN
    dbo.TableA2 as A2 INNER JOIN dbo.TableB2 as B2 ON A2.ID = B2.ID
ON A1.ID = A2.ID and A1.AnotherID = A2.AnotherID

My question would be:

As both of the subqueries are basic select type queries, is it possible to rewrite the query as I have done above?

Answer 1

The equivalent query would look like this:

SELECT . . .   -- select the columns you want
FROM  (dbo.TableA1 A1 INNER JOIN
       dbo.TableB1 B1
       ON A1.ID = B1.ID
      ) FULL OUTER JOIN
      (dbo.TableA2 A2 INNER JOIN
       dbo.TableB2 B2
       ON A2.ID = B2.ID
      )
      ON A1.ID = A2.ID AND
         ?1.AnotherID = ?2.AnotherID

The ? are because I don't know if AnotherID is in the "A" or "B" table.