PB using UNION ALL with VB6 and SQL-server

I'm working on a softwear and I have to create some Update. This softwear used first MS Access as a database, and now I have to create the code which allows it to use MS SQL-server. This softwear is created in VB6.

I've got some error when I'm using the UNION ALL function. This error appears:
"incorrect syntax towards the key word ' union' "

Here is the code in VB6 :

" GOpenLocalDb (FOR_READ) ' open the database

SQLStmt = "select * from ol_table_temp"
SQLStmt = SQLStmt & " where [Subject_no] = " & dlr_subject & " "
ord$ = SQL_Order()
SQLStmt = SQLStmt & ord$

'dalafouzos: 24/09/2002 I added the lines below to include the DLR entries in the ol_old table
SQLStmt = SQLStmt & " union all select * from ol_table_old where [Subject_no] = " & dlr_subject & " "
ord$ = SQL_Order()
SQLStmt = SQLStmt & ord$

'GOpenLocalDb (FOR_READ) ' open the database
Set DLRset = New ADODB.Recordset
DLRset.CursorLocation = adUseClient
DLRset.Open SQLStmt, g_objConn, adOpenKeyset, adLockReadOnly, adCmdText "

when the error appears the value of SQLStmt is :

"select * from ol_table_temp where [Subject_no] = 1020 Order by [Date] DESC, [Time] DESC union all select * from ol_table_old where [Subject_no] = 1020 Order by [Date] DESC, [Time] DESC "

Thanks for your help...and both tables has the same DDL?|||I think so. Both of them are similar...but how can I see if they have the same DDL? because I'm not sure as I didn't have to create these tables.

But this syntaxe works well with MS Access...the problem appears only with MS SQL-server.sql