Dynamic internal table operation in sap abap

      DATA : lv_string TYPE string.
      CLEAR lv_string.
      IF wds_nbr IS NOT INITIAL.
        CONCATENATE lv_string 'wds_nbr = wds_nbr' INTO lv_string.
      ENDIF.

      IF sap_nbr IS NOT INITIAL.
        IF lv_string IS NOT INITIAL.
          CONCATENATE lv_string 'and' 'sap_nbr = sap_nbr' INTO lv_string  SEPARATED BY space.
        ELSE.
          CONCATENATE lv_string 'sap_nbr = sap_nbr' INTO lv_string.
        ENDIF.
      ENDIF.

      IF charg IS NOT INITIAL.
        IF lv_string IS NOT INITIAL .
          CONCATENATE lv_string 'and' 'charg = charg' INTO lv_string  SEPARATED BY space.
        ELSE.
          CONCATENATE lv_string 'charg = charg' INTO lv_string.
        ENDIF.
      ENDIF.

      IF werks IS NOT INITIAL.
        IF lv_string IS NOT INITIAL .
          CONCATENATE lv_string 'and' 'werks = werks' INTO lv_string  SEPARATED BY space.
        ELSE.
          CONCATENATE lv_string 'werks = werks' INTO lv_string.
        ENDIF.
      ENDIF.

      IF rol_no IS NOT INITIAL.
        IF lv_string IS NOT INITIAL .
          CONCATENATE lv_string 'and' 'rol_no in r_rol_no' INTO lv_string  SEPARATED BY space.
        ELSE.
          CONCATENATE lv_string 'rol_no in r_rol_no' INTO lv_string.
        ENDIF.
      ENDIF.
      SELECT * FROM zmm_stagrpriinfo INTO TABLE it_stagtab WHERE (lv_string).