Select * From ЗапросА
Union All
Select * From ЗапросБ

Select [Запрос1].[ЛюбоеПоле] From Запрос1

Public Sub CreateDeliriumTremens()
    Dim db As Database
    Set db = CurrentDb
    
    Dim tds As TableDefs
    Set tds = db.TableDefs
    
    Dim td As TableDef
    
    Set td = db.CreateTableDef( "Таблица1" )
        td.Fields.Append td.CreateField( "ID" , dbLong)
        td.Fields.Append td.CreateField( "a" , dbLong)
        td.Fields.Append td.CreateField( "b" , dbText)
        td.Fields.Append td.CreateField( "c" , dbDouble)
    tds.Append td
    
    Set td = db.CreateTableDef( "Таблица2" )
        td.Fields.Append td.CreateField( "ID" , dbLong)
        td.Fields.Append td.CreateField( "a" , dbLong)
        td.Fields.Append td.CreateField( "b" , dbText)
        td.Fields.Append td.CreateField( "c" , dbDouble)
    tds.Append td
    
    db.CreateQueryDef  "Запрос1" ,  "Select 1  As [TableID], a, b, Sum(c) As d " & _
         "From [Таблица1] Group By 1 ,a,b"
    db.CreateQueryDef  "Запрос2" ,  "Select 2  As [TableID], a, b, Sum(c) As d " & _
         "From [Таблица2] Group By 2 ,a,b"
    db.CreateQueryDef  "Запрос3" ,  "Select * From [Запрос1] "  & _
         "Union All Select * From [Запрос2]" 
    db.CreateQueryDef  "Запрос_Глючный" ,  "Select TableID, a, b From [Запрос3]" 
    db.CreateQueryDef  "Запрос_Работающий" ,  "Select TableID, a, b, d From [Запрос3]" 
    
    Set td = Nothing
    Set tds = Nothing
    Set db = Nothing
End Sub