oracle function 的简单问题，求教

[Vash]

新人请教……
create or replace function f_test1
(i_aa test3.aa%type,
i_bb test3.bb%type
)
return varchar2
is
v_result varchar2(20);
count_1 number;
begin
select t3.cc into v_result from test3 t3
where
t3.aa = i_aa
and t3.bb = i_bb
;
if v_result is null then
return '1010';
end if
;
return v_result;
end f_test1;

想达到的效果是 ，如果t3关联不到数据时，能返回 ‘1010’，
但是实际 上 并没有返回‘1010’；而是 返回了 空。
请问是怎么回事呢？

[linwaterbin]

create or replace function f_test1
(i_aa test3.aa%type,
i_bb test3.bb%type
)
return varchar2
is
v_result varchar2(20);
count_1 number;
begin
  select t3.cc into v_result  from test3 t3
 where
     t3.aa = i_aa
 and t3.bb = i_bb
;
return v_result;
exception 
    when others then
    return '1010';
end f_test1;

u1@EMREP> select * from test3;

        AA         BB         CC
---------- ---------- ----------
                      1          2          3

u1@EMREP> call f_test1(1,1) into :a;

Call completed.

u1@EMREP> print a;

         A
----------
      1010

u1@EMREP> call f_test1(1,2) into :a;

Call completed.

u1@EMREP> print a;

         A
----------
         3

[Vash]

这么晚了……先谢过你的回复。马上去试试…… Orz