SQL: exception handling in a function - oracle

Question

I have encountered a rather mysterious problem today. As I executed my SQL function f_interestrate()( which should raise a from me defined exception when one of the parameters is equal to 0 ) with the following parameters:
SELECT GENERAL_FUNCTIONS.F_INTERESTRATE(2500000, 0.10, 0) FROM dual;
Gave me the following error:
ORA-06503: PL/SQL: Function returned without value
ORA-06512: at "NOAHBASE.GENERAL_FUNCTIONS", line 73
06503. 00000 - "PL/SQL: Function returned without value"
*Cause: A call to PL/SQL function completed, but no RETURN statement was executed.
*Action: Rewrite PL/SQL function, making sure that it always returns
a value of a proper type.
But as you may see in the following code sample the function should instead raise the form me defined exception ex_invalid_devisor. Not forget to mention that this function is nested inside a package.
FUNCTION f_interestrate(pn_principal NUMBER, pn_interest NUMBER, pn_years NUMBER) RETURN NUMBER IS
vn_interestrate NUMBER;
ex_invalid_devisor EXCEPTION;
BEGIN
IF pn_principal = 0 OR
pn_interest = 0 OR
pn_years = 0 THEN
RAISE ex_invalid_devisor;
ELSE
vn_interestrate := ((pn_interest/pn_principal)-1)/pn_years;
RETURN vn_interestrate;
END IF;
EXCEPTION
WHEN ex_invalid_devisor THEN
DBMS_OUTPUT.PUT_LINE('Devisor must be bigger then 0');
END;
Am I doing anything wrong?

Answer 1

This is how you should handle ... I added 'return -1' in your code. HTH.
create or replace FUNCTION f_interestrate(pn_principal NUMBER, pn_interest NUMBER, pn_years NUMBER) RETURN NUMBER IS
vn_interestrate NUMBER;
ex_invalid_devisor EXCEPTION;
BEGIN
IF pn_principal = 0 OR
pn_interest = 0 OR
pn_years = 0 THEN
RAISE ex_invalid_devisor;
ELSE
vn_interestrate := ((pn_interest/pn_principal)-1)/pn_years;
RETURN vn_interestrate;
END IF;
EXCEPTION
WHEN ex_invalid_devisor THEN
DBMS_OUTPUT.PUT_LINE('Devisor must be bigger then 0');
return -1;
END;
SQL> select F_INTERESTRATE(2500000, 0.10, 0) FROM dual;
F_INTERESTRATE(2500000,0.10,0)
------------------------------
-1

Answer 2

As PL/SQL already has a perfectly good zero_divide exception, I'd be tempted to just write the function as:
create or replace function f_interestrate
( pn_principal number
, pn_interest number
, pn_years number )
return number
as
begin
return ((pn_interest / pn_principal) - 1) / pn_years;
end;
then you'll get the default failure message:
SQL> select f_interestrate(2500000, 0.10, 0) from dual;
select f_interestrate(2500000, 0.10, 0) from dual
*
ERROR at line 1:
ORA-01476: divisor is equal to zero
ORA-06512: at "XXX.F_INTERESTRATE", line 8
Or if you really need some customised handling,
create or replace function f_interestrate
( pn_principal number
, pn_interest number
, pn_years number )
return number
as
begin
return ((pn_interest / pn_principal) - 1) / pn_years;
exception
when zero_divide then
[[[ do something here ]]]
end;
I notice you also raise your custom ex_invalid_devisor exception when pn_interest is zero, even though this isn't used as a divisor, so perhaps there is some subtle logic I am missing here.
(Edit: thinking about it, if pn_interest is zero then maybe you just need to return pn_principal regardless.)