Is no-data-found exception not raised implicitly? - oracle

Question

question 1:
I noticed the no-data-found exception not raised implicitly, do we need to raise them manually/explicitly?
Question 2:
I writing a SP package with 4 procedures in it and i'm writing below procedures on a single table.
the exception handling is repetitive in each procedure. is there any guidance/coding standard to keep it in a single place procedure#5 or function and call it there.
Select
Update
Insert
Delete
I guess if I keep it in a function it would raise the exception and return to the called procedure and continue to run ? but when we raise a exception the program should stop , right?

Answer 1

You have run into the only exception in PL/SQL exception handling - ORA-1403: no data found is suppressed when it is generated by a function called in a SQL context.
No data found exceptions work fine in PL/SQL anonymous blocks:
SQL> declare
2 v_number number;
3 begin
4 select 1 into v_number from dual where 1=0;
5 end;
6 /
declare
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 4
And no data found also works as expected with a function called in a PL/SQL statement:
SQL> create or replace function exception_no_data_found return number is
2 v_number number;
3 begin
4 select 1 into v_number from dual where 1=0;
5 return v_number;
6 end;
7 /
Function created.
SQL> declare
2 v_number number;
3 begin
4 v_number := exception_no_data_found;
5 end;
6 /
declare
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "JHELLER.EXCEPTION_NO_DATA_FOUND", line 4
ORA-06512: at line 4
But when calling the function in a SQL context, the exception disappears:
SQL> select exception_no_data_found from dual;
EXCEPTION_NO_DATA_FOUND
-----------------------
I think the reason for this is that SQL internally uses the no data found exception to let the system know there are no more rows, so it's not always an exception. (This behavior is probably a bug but has been around for so long that it'll never change.)
To raise that exception in this situation, you must manually catch and raise a different exception like this:
SQL> create or replace function exception_no_data_found return number is
2 v_number number;
3 begin
4 select 1 into v_number from dual where 1=0;
5 return v_number;
6 exception when no_data_found then
7 raise_application_error(-20000, 'No data found.');
8 end;
9 /
Function created.
SQL> select exception_no_data_found from dual;
select exception_no_data_found from dual
*
ERROR at line 1:
ORA-20000: No data found.
ORA-06512: at "JHELLER.EXCEPTION_NO_DATA_FOUND", line 7
But the above situation is by far the weirdest part about Oracle exception handling. Other than this scenario, in general you are almost always better off by not doing any exception handling. Just let the program break; the exceptions will propagate up, and the application will get an exception that includes the full error message and the exact line number of the error. In practice, that information is almost always enough to debug any problems. Only add custom exception handling when you know for sure that you need to gather extra data.