[GENERAL] cursor return null

[Ramesh T]

Hello,
           in postgres function (id bigint ),the following code not return
any value with artNums ,But when i do  select statement ony it's output the
values with out include cursor

 i.e,cursor problem ..?

please let me know what should i do to getvalues from cursor, but i dont
where i missing

 function (id bigint )

DECLARE
      PartNums   varchar (10000);
 artNums CURSOR for
      SELECT p.PART_NUM part_num
        FROM lineitem sol, part p
       WHERE sol.ORDER_ID = id AND p.PART_ID = sol.PART_ID;

   BEGIN
      FOR cPart IN  artNums LOOP
   BEGIN
        PartNums := PartNums || cPart.part_num || ', ';
END;