exception handling not outputting to dbms - sql

Question

Here is my sql code for a function that calculates the area of a circle. I am having trouble getting a dbms_output to show the user defined exception.
I begin by declaring an exception underzero. then i raise it if the user inputs a number less than or equal to 0. In the exception i have dbms_output then return the result. It shows in the query result that the value is null, however the output isn't showing.
I have already set serveroutput on and set verify off. I don't know why it wont output anything. If i run that line alone it outputs to the dbms output window but not when the exception is raised.
create or replace function circle_area
(p_radius number)
return number
is
c_Pi Constant number := acos(-1);
v_result number(10, 2);
underzero exception;
begin
if p_radius <=0 then
raise underzero;
else
v_result := c_pi * p_radius * p_radius;
return v_result;
end if;
exception
when underzero then
dbms_output.put_line('enter number greater than 0');
return v_result;
when others then
dbms_output.put_line('Exception Location: Anonymous Block');
dbms_output.put_line(sqlcode || ': ' || sqlerrm);
return v_result;
end circle_area;
to call the function:
select circle_area(-2) from dual;

Answer 1

I'm not sure that I understand the problem. The code you posted will generate output to dbms_output if serveroutput is enabled...
SQL> set serveroutput on;
SQL> create or replace function circle_area
2 (p_radius number)
3 return number
4 is
5 c_Pi Constant number := acos(-1);
6 v_result number(10, 2);
7 underzero exception;
8 begin
9 if p_radius <=0 then
10 raise underzero;
11 else
12 v_result := c_pi * p_radius * p_radius;
13 return v_result;
14 end if;
15
16 exception
17 when underzero then
18 dbms_output.put_line('enter number greater than 0');
19 return v_result;
20 when others then
21 dbms_output.put_line('Exception Location: Anonymous Block');
22 dbms_output.put_line(sqlcode || ': ' || sqlerrm);
23 return v_result;
24 end circle_area;
25 /
Function created.
SQL> select circle_area(-2) from dual;
CIRCLE_AREA(-2)
---------------
enter number greater than 0
I'm assuming that this is part of a homework assignment and not a real problem that you're facing. In reality, you'd never write code whose primary purpose was to write to dbms_output and you would never, ever have an exception handler that only wrote to dbms_output.