select *
          from example  a 
          where
        ((a.VALIDFROMDATE between TO_DATE ('01.12.28', 'dd.mm.yy') AND TO_DATE ('01.01.29', 'dd.mm.yy'))
      or (a.VALIDTODATE between TO_DATE ('01.12.28', 'dd.mm.yy') AND TO_DATE ('01.01.29', 'dd.mm.yy')
      or ((a.VALIDFROMDATE <= TO_DATE ('01.12.28', 'dd.mm.yy')) AND a.VALIDFROMDATE is null)))
         
         order by a.VALIDFROMDATE desc;