SAP ABAP SELECT MAX

DATA :ZCMISNO_M(30) TYPE C.
LOOP AT ALV_OUT WHERE ZCMISNO = ‘’.
CLEAR ZCMISNO_M.
SELECT MAX( ZCMISOD ) INTO ZCMISNO_M FROM ZCMISTHQ00130 WHERE ZERPORDERNO = ALV_OUT-EBELN.
IF ZCMISNO_M IS NOT INITIAL.
SELECT SINGLE ZCMISNO INTO ALV_OUT-ZCMISNO FROM ZCMISTHQ00090 WHERE ZCMISOD = ZCMISNO_M.
ENDIF.
MODIFY ALV_OUT.
ENDLOOP.