Pipelined function usage

 CREATE or replace TYPE tree_ot AS OBJECT(
CUST_ACCOUNT_ID  NUMBER(15),    
account_name               VARCHAR2(240) ,
account_number    VARCHAR2(240));

create or replace type tree_tt as table of tree_ot;

create or replace function f_tree

   return tree_tt pipelined

is

   l_retval tree_ot := tree_ot (null, null, null);

begin

   for r_dept in (select cust_account_id,account_name,account_number  from hz_cust_accounts where rownum<30 )

    loop

        l_retval.CUST_ACCOUNT_ID :=r_dept.CUST_ACCOUNT_ID;

        l_retval.account_name :=r_dept.account_name;

        l_retval.account_number :=r_dept.account_number;    

         pipe row(l_retval);

   end loop;

   return;

end;

select * from table(f_tree)