Handling exception 1) when defining Oracle function 2) When Calling Oracle function - oracle

Question

My Oracle function below(code1) have no exception handling.
Therefore if it is called(code2) with 0, error shows.
--Code 1
CREATE OR REPLACE FUNCTION TEST2
(P1 IN VARCHAR2)
RETURN NUMBER AS V_VALUE NUMBER;
BEGIN
SELECT(
SELECT 1/TO_NUMBER(P1)
FROM DUAL
)
INTO V_VALUE
FROM DUAL;
RETURN V_VALUE;
END;
/
--Code2
SELECT TEST2('0') FROM DUAL;
Please, help to add exception handling for each 1) 2) case as below.
case 1) when defining function, how to modify code1
for function to return -1 if a system exception,
including dividing by zero happen?
case 2) Without adding exception in my Oracle funtion,
how to modify code2 for the reslut to be -1 if a system excetion, including dividing zero happens in the function?

Answer 1

I think you are making this more complicated than it needs to be. I did not compile this code below, but should provide as an example. Regarding exceptions, it is OK to handle divide-by-zero, but hiding all other exception types is very, very bad design. Also, if I pass in test2(-1), then the result will be a valid value of -1. Are you assured your input parameter is always positive. Regardless, here is a solution which checks for a 0 parameter, and avoids the division problem. A better solution is to define TEST1 P1 as a NUMBER to begin with, and let the caller format it as needed. If not, I could pass in something like TEST2('fsfd') and get an exception.
CREATE OR REPLACE FUNCTION TEST2(P1
IN VARCHAR2)
RETURN NUMBER;
D_Result NUMBER : = -1;
BEGIN
IF P1 <> 0 THEN
D_result := 1/TO_NUMBER(P1);
END IF;
RETURN D_Result;
END
If you really want to throw a divide error, you can catch is like this:
DECLARE
result NUMBER;
BEGIN
result := test2(0);
EXCEPTION
WHEN OTHERS THEN
result := -1;
END;

Answer 2

#OldProgrammer shows how to prevent the exception from occurring, which is the best choice. However, if you want to allow the exception to occur and catch it in the function you could use:
CREATE OR REPLACE FUNCTION TEST2(P1 IN VARCHAR2)
RETURN NUMBER
AS
V_VALUE NUMBER;
BEGIN
BEGIN
V_VALUE := 1 / TO_NUMBER(P1);
EXCEPTION
WHEN OTHERS THEN
V_VALUE := -1;
END;
RETURN V_VALUE;
END TEST2;
or you could simplify this to
CREATE OR REPLACE FUNCTION TEST2(P1 IN VARCHAR2)
RETURN NUMBER
AS
BEGIN
RETURN 1 / TO_NUMBER(P1);
EXCEPTION
WHEN OTHERS THEN
RETURN -1;
END TEST2;