Select * FROM Kundenstammdaten INNER JOIN UBR On Kundenstammdaten.KundenID = _
  UBR.SparteID 
Where UBR.Unfrent = " & WertUnfallrente & " UNION Select * FROM Kundenstammdaten 
INNER JOIN UNFALL On Kundenstammdaten.KundenID = UNFALL.SparteID Where _
  Unfall.UNFRENT = " & WertUnfallrente & "