SELECT Rut,
       LEFT(Rut,CHARINDEX('-',Rut)-1) Rut_Sin_DV
FROM dbo.YourTable;

SELECT Rut,
       CASE
           WHEN CHARINDEX('-',Rut) > 0 THEN LEFT(Rut,CHARINDEX('-',Rut)-1) Rut_Sin_DV
           ELSE Rut
       END Rut_Sin_DV
FROM dbo.YourTable;