SELECT
    X.A_Id,
    X.A_Name,
    X.B_Id,
    X.B_Name,
    X.C_Id,
    X.C_Name
FROM
(
    SELECT
        dbo.A.Id AS A_Id,
        dbo.A.Name AS A_Name,
        NULL AS B_Id,
        NULL AS B_Name,
        dbo.C.Id AS C_Id,
        dbo.C.Name AS C_Name
    FROM
        dbo.A  CROSS JOIN dbo.C
) AS X
EXCEPT
(
    SELECT
        dbo.A.Id AS A_Id,
        dbo.A.Name AS A_Name,
        NULL AS B_Id,
        NULL AS B_Name,
        dbo.C.Id AS C_Id,
        dbo.C.Name AS C_Name
    FROM
        dbo.A
            INNER JOIN dbo.B ON dbo.A.Id = dbo.B.AId
            INNER JOIN dbo.C ON dbo.B.CId = dbo.C.Id
 )