ABAP遍历结构字段

try.
        create data dref type (dbtab).
        assign dref->* to <wa>.
        select *
               from (dbtab) up to rows rows
               into <wa>.
          do.
            assign component sy-index
                   of structure <wa> to <comp>.
            if sy-subrc = 0.
              write / <comp>.
            else.
              exit.
            endif.
          enddo.
          uline.
        endselect.
      catch cx_sy_create_data_error.
        write 'Error in data creation'.
    endtry.