select  d.nnum     ,
        d.cstatus  ,
        d.nordernum,
        c.dregdate ,
        c.nmoney

  from  t_b c,
       (
        select  a.nnum     ,
                a.cstatus  ,
                nordernum  = max(b.nordernum)
          from  t_a a,
                t_b b
         where  a.nnum     = b.nnum
        group by
                a.nnum     ,
                a.cstatus
       ) d
 where  c.nnum      =  d.nnum
   and  c.nordernum =  d.nordernum
order by
        d.nnum