Функция поиска документа для Супермага : Oracle

FUNCTION  LAST_PRIH(LOC IN INTEGER, ART IN VARCHAR2,SYSOP IN INTEGER, USOP IN INTEGER)
RETURN VARCHAR2
IS
 L_DOCNUM VARCHAR2(50);
BEGIN
   L_DOCNUM:='';
   IF USOP IS NULL
   THEN
      SELECT NVL(ID,0) INTO L_DOCNUM
   FROM (SELECT A2.CREATEDAT,
               A2.ID,
               A2.LOCATIONTO,
               B2.ARTICLE,
               B2.ITEMPRICE ITEMPRICE,
               B2.QUANTITY,
               B2.TOTALPRICE,
               ROW_NUMBER() OVER(PARTITION BY B2.ARTICLE ORDER BY A2.CREATEDAT DESC) RN
    FROM SUPERMAG.SMDOCUMENTS A2, SUPERMAG.SMSPEC B2
    WHERE A2.DOCTYPE = B2.DOCTYPE
           AND A2.ID = B2.DOCID
		   AND A2.OPCODE=SYSOP
           AND A2.DOCSTATE = 3
           AND A2.LOCATIONTO = LOC
           AND A2.DOCTYPE = 'WI'
           AND B2.ARTICLE =ART)
   WHERE RN = 1;
   ELSE
    SELECT NVL(ID,0) INTO L_DOCNUM
    FROM (SELECT A2.CREATEDAT,
               A2.ID,
               A2.LOCATIONTO,
               B2.ARTICLE,
               B2.ITEMPRICE ITEMPRICE,
               B2.QUANTITY,
               B2.TOTALPRICE,
               ROW_NUMBER() OVER(PARTITION BY B2.ARTICLE ORDER BY A2.CREATEDAT DESC) RN
    FROM SUPERMAG.SMDOCUMENTS A2, SUPERMAG.SMSPEC B2
    WHERE A2.DOCTYPE = B2.DOCTYPE
           AND A2.ID = B2.DOCID
		   AND A2.OPCODE=SYSOP
		   AND A2.USEROP=USOP
           AND A2.DOCSTATE = 3
           AND A2.LOCATIONTO = LOC
           AND A2.DOCTYPE = 'WI'
           AND B2.ARTICLE =ART)
    WHERE RN = 1;
	END IF;
 RETURN L_DOCNUM;
END;

AND A2.LOCATIONTO = LOC

   
AND NVL(A2.LOCATIONTO,A2.LOCATIONFROM) = LOC

AND A2.DOCTYPE='WI'