UPDATE a
   SET (code1, code2) =
          (SELECT DECODE (a.order_no, NULL, b.cd1, c.no1) code1,
                  DECODE (a.order_no, NULL, b.cd2, c.no2) code1
             FROM b, c
            WHERE a.sell_no = b.sell_no(+) AND a.order_no = c.order_no(+)
                  AND c.index = '1')
 WHERE a.code1 IS NULL AND a.code2 IS NULL

update
    (select
        a.code1    old_code1,
        a.code2    old_code2,
        decode(a.order_no,null,b.cd1, c.no1)    new_code1,
        decode(a.order_no,null,b.cd2, c.no2)    new_code2
     from
         b,c
     where
         a.sell_no = b.sell_no(+) 
     and    a.order_no = c.order_no(+) 
     and    c.index = '1'
     and    a.code1 is null
     and    a.code2 is null
    )
set
    old_code1 = new_code1,
    old_code2 = new_code2

UPDATE a 
   SET (code1, code2) = 
          (SELECT DECODE (a.order_no, NULL, b.cd1, c.no1) code1, 
                  DECODE (a.order_no, NULL, b.cd2, c.no2) code1 
             FROM a,b, c 
            WHERE a.sell_no = b.sell_no(+) AND a.order_no = c.order_no(+) 
                  AND c.index = '1'
                  and a.code1 IS NULL AND a.code2 IS NULL ) 
 WHERE a.code1 IS NULL AND a.code2 IS NULL 

UPDATE 
        A SET ( CODE1 , 
                CODE2 ) = ( 
        SELECT 
                CODE1 , 
                CODE2 
        FROM 
                ( 
                SELECT 
                        A.SELL_NO NOS , 
                        B.CD1 CODE1 , 
                        B.CD2 CODE2 
                FROM 
                        A , 
                        B 
                WHERE 
                        A.ORDER_NO IS NULL 
                        AND A.SELL_NO=B.SELL_NO 
                UNION 
                SELECT 
                        A.SELL_NO NOS , 
                        C.NO1 CODE1 , 
                        C.NO2 CODE2 
                FROM 
                        A , 
                        C 
                WHERE 
                        A.ORDER_NO IS NOT NULL 
                        AND A.ORDER_NO=C.ORDER_NO 
                        AND C.INDEXS=1 ) D 
        WHERE 
                A.SELL_NO=D.NOS ) 
WHERE 
        A.CODE1 IS NULL 
        AND A.CODE2 IS NULL