create table column_list_test
( myid number
,mydesc varchar2(20)
,myname varchar2(100)
,mydate date
);

DECLARE
v_table_name varchar2(30) := 'column_list_test';
TYPE v_column_names_type IS TABLE OF varchar2(30) INDEX BY BINARY_INTEGER;
v_column_names v_column_names_type;
v_index BINARY_INTEGER;
v_col_list varchar2(4000);
BEGIN
--initialize table-names-array
FOR currow in (select column_id,column_name
from user_tab_columns
where 1=1
and table_name = upper(v_table_name)
order by table_name,column_id)
LOOP
v_column_names(currow.column_id) := currow.column_name;
END LOOP;

-- loop through the names-array
v_index := v_column_names.first;
while v_index is not NULL loop

dbms_output.put_line(v_index || ' - ' ||v_column_names(v_index));
v_col_list := v_col_list || v_column_names(v_index);

-- next index:
v_index := v_column_names.next (v_index);

-- add a comma only if it is not the last attribute.
if nvl(v_index,0) <> 0 then
v_col_list := v_col_list ||',';
end if;
end loop;

--complete col-list comma separated for further dynamic-sql...
dbms_output.put_line(v_col_list);