SAP HANA STRING_AGG

DROP PROCEDURE ""."ZCONCAT_EKKO_EBN";
CREATE PROCEDURE ""."ZCONCAT_EKKO_EBN"(OUT RESULT ""."OUT_SPLIT_EK_EBN")
LANGUAGE SQLSCRIPT AS
BEGIN
    DECLARE _ZHETONG NVARCHAR(1000) ARRAY;
    DECLARE _ZEBELN  NVARCHAR(5000) ARRAY;
    DECLARE _ZHT NVARCHAR(1000); 
 
    DECLARE _INDEX INTEGER := 1;
    DECLARE _IND1 INTEGER := 1;
 
    DECLARE CURSOR C_CURSOR1 FOR
      SELECT DISTINCT ZHETONG,EBELN FROM "CTNT_ECC"."EKKO" WHERE BUKRS LIKE '21%' AND ZHETONG NOT IN ('','','','TS','无')
      ORDER BY ZHETONG,EBELN;
    FOR CUR_ROW1 AS C_CURSOR1 DO 
 
      IF _IND1 = 1 THEN
        _ZHT := CUR_ROW1.ZHETONG;
        _ZHETONG[:_INDEX] := '';
        _ZEBELN[:_INDEX] := '';
      END IF; 
 
      IF CUR_ROW1.ZHETONG = :_ZHT THEN
       _ZHETONG[:_INDEX] := CUR_ROW1.ZHETONG;
       _ZEBELN[:_INDEX] := :_ZEBELN[:_INDEX]||CUR_ROW1.EBELN||',';
      ELSE
      _INDEX := :_INDEX + 1;
      _ZHETONG[:_INDEX]  := CUR_ROW1.ZHETONG;
      _ZEBELN[:_INDEX] := CUR_ROW1.EBELN ||',';
      _ZHT := CUR_ROW1.ZHETONG;
      END IF;
 
       _IND1 := :_IND1 + 1;
    END FOR;  
 
      RST = UNNEST(:_ZHETONG, :_ZEBELN) AS ("ZHETONG", "EBELN");
 
      RESULT = SELECT ZHETONG,
                      LEFT(EBELN,LENGTH(EBELN)-1) AS EBELN
                 FROM :RST;
 
END;
 
CALL "ZB_CHENWH"."ZCONCAT_EKKO_EBN"(?) ;