Compex SQL Query containing UNION, Needs Filtering

[ticktack]

Hi there,

I am trying to do a UNION with slightly different queries, it appears to work but it now bring in another problem. The second part of the UNION need to have a an extra field value ("NULL") added thus to match the number of fields between the two select queries. The problem comes that I some have duplicate records and want to condense them down so that "Table_Form_Element_ID" has a single record against it but I want the record to be the one where (NOT (Form_Element_Server_Process_Code IS NULL)) AND (NOT (Form_Element_Site_Id IS NULL)) and disregard the other bogus records. However say this if (NOT (Form_Element_Server_Process_Code IS NULL)) AND (NOT (Form_Element_Site_Id IS NULL)) do not exist then display the records (NOT (Form_Element_Server_Process_Code IS NULL)) OR
(NOT (Form_Element_Site_Id IS NULL)).

The current query is producing the following:-

 
SELECT Form_Storage_Process_Order, Form_Element_Server_Process_Code, Table_Form_Element_ID, Table_Form_Table_Name, Table_Form_Element_Key, Table_Form_Element_Name, Table_Form_Element_Type, Table_Form_Element_Length, Form_Element_Site_Id, Form_Id
FROM (SELECT cTbl.Form_Storage_Process_Order AS Form_Storage_Process_Order, cTbl.Form_Element_Server_Process_Code AS Form_Element_Server_Process_Code, dTbl.Table_Form_Element_ID AS Table_Form_Element_ID, dTbl.Table_Form_Table_Name AS Table_Form_Table_Name, dTbl.Table_Form_Element_Key AS Table_Form_Element_Key, dTbl.Table_Form_Element_Name AS Table_Form_Element_Name, dTbl.Table_Form_Element_Type AS Table_Form_Element_Type, dTbl.Table_Form_Element_Length AS Table_Form_Element_Length, bTbl.Form_Element_Site_Id AS Form_Element_Site_Id, eTbl.Form_Id AS Form_Id
     FROM WWWFORM_SITE_ELEMENT_LAYOUT aTbl INNER JOIN
        WWWFORM_SITE_ELEMENT bTbl ON aTbl.Form_Element_Site_Id = bTbl.Form_Element_Site_Id INNER JOIN
        WWWDATABASE_STORAGE_PROSESS_GROUP cTbl ON aTbl.Form_Element_Layout_Id = cTbl.Form_Element_Layout_Id INNER JOIN
        WWWDATABASE_STORAGE_PROSESS_STRUCTURE dTbl ON cTbl.Table_Form_Element_ID = dTbl.Table_Form_Element_ID INNER JOIN
        WWWFORM eTbl ON eTbl.Form_Storage_Process_Type_Id = cTbl.Form_Storage_Process_Type_Id
     UNION
     SELECT cTbl.Form_Storage_Process_Order AS Form_Storage_Process_Order, 
       cTbl.Form_Element_Server_Process_Code AS Form_Element_Server_Process_Code, 
       dTbl.Table_Form_Element_ID AS Table_Form_Element_ID, dTbl.Table_Form_Table_Name AS Table_Form_Table_Name, 
       dTbl.Table_Form_Element_Key AS Table_Form_Element_Key, dTbl.Table_Form_Element_Name AS Table_Form_Element_Name, 
       dTbl.Table_Form_Element_Type AS Table_Form_Element_Type, dTbl.Table_Form_Element_Length AS Table_Form_Element_Length, NULL, 
       eTbl.Form_Id AS Form_Id
     FROM WWWDATABASE_STORAGE_PROSESS_GROUP cTbl INNER JOIN
         WWWDATABASE_STORAGE_PROSESS_STRUCTURE dTbl ON cTbl.Table_Form_Element_ID = dTbl.Table_Form_Element_ID INNER JOIN
         WWWFORM eTbl ON eTbl.Form_Storage_Process_Type_Id = cTbl.Form_Storage_Process_Type_Id) DERIVEDTBL
WHERE (NOT (Form_Element_Server_Process_Code IS NULL)) OR (NOT (Form_Element_Site_Id IS NULL)) AND (Form_Id = '1')
 

If anyone knows how I can get around this problem I would be very grateful. Its giving me a headache. I am not familiar with If Else Clauses in SQL but I feel that it must be possible.

Thanks