What exact exception to be caugth while calling TO_DATE in pl/sql code - oracle

Question

I have below code to_date('1311313', 'yymmdd') which actually throws exception with saying invalid month. Which is can manage as
exception
when others then
sop('date format is wrong');
Here the problem is everything will get caught which I do not want to do as if some other error will occur then also it will pass the message date format is wrong. I also do not want to create a user defined exception. Just want to know which exception is being thrwon out so that I can use in my code like below
exception
when name_of_exception then
sop('date format is wrong');

Answer 1

The Internally Defined Exceptions section of the Oracle Database PL/SQL Language Reference says:
An internally defined exception does not have a name unless either PL/SQL gives it one (see "Predefined Exceptions") or you give it one.
You code throws the exception ORA-01830:
SQL> select to_date('1311313', 'yymmdd') from dual
*
ERROR at line 1:
ORA-01830: date format picture ends before converting entire input string
Since it is not one of the Predefined Exceptions, you must give it a name yourself:
declare
ex_date_format exception;
pragma exception_init(ex_date_format, -1830);
v_date date;
begin
select to_date('1311313', 'yymmdd')
into v_date
from dual;
exception
when ex_date_format then
sop('date format is wrong');
end;
/

Answer 2

There are at least two approaches to handle different exceptions raised during an attempt to convert character literal to a value of DATE data type:
Define as many exception names and associate them with Oracle error codes, using exception_init pragma, as many exceptions to_date() function is able to raise.
Create a stand alone, or part of a package, wrap-up function for to_date() function, with one when others exception handler.
Personally I lean toward the second one.
SQL> create or replace package util1 as
2 function to_date1(
3 p_char_literal in varchar2,
4 p_date_format in varchar2
5 ) return date;
6 end;
7 /
Package created
SQL> create or replace package body util1 as
2
3 function to_date1(
4 p_char_literal in varchar2,
5 p_date_format in varchar2
6 ) return date is
7 begin -- in this situation it'll be safe to use `when others`.
8 return to_date(p_char_literal, p_date_format);
9 exception
10 when others then
11 raise_application_error(-20001, 'Not a valid date');
12 end;
13
14 end;
15 /
Package body created
Now, there is only one exception to handle, -20001 Not a valid date, and your PL/SQl block might look like this:
SQL> set serveroutput on;
-- [1] otherwise, for '1311313' the ORA-01830 exception would be raised
SQL> declare
2 not_a_valid_date exception;
3 pragma exception_init(not_a_valid_date, -20001);
4 l_res date;
5 begin
6 l_res := util1.to_date1('1311313', 'yymmdd');
7 exception
8 when not_a_valid_date then
9 dbms_output.put_line(sqlerrm);
10 -- or other handler sop('date format is wrong');
11 end;
12 /
ORA-20001: Not a valid date
-- [2] otherwise, for '000000' the ORA-01843(not a valid month)
-- exception would be raised
SQL> declare
2 not_a_valid_date exception;
3 pragma exception_init(not_a_valid_date, -20001);
4 l_res date;
5 begin
6 l_res := util1.to_date1('000000', 'yymmdd');
7 exception
8 when not_a_valid_date then
9 dbms_output.put_line(sqlerrm);
10 -- or other handler sop('date format is wrong');
11 end;
12 /
ORA-20001: Not a valid date