How to catch date errors and continue processing in a PL/SQL procedure

Question

I'm updating a date field with dates constructed from day, month and year fields. The incoming data has many instances of day and month that are not valid dates, ex 11 31 2007. There is no 31st day in November.
I would like to write a pl/sql script to scan the table containing these values and log the rows that produce conversion errors.
I thought I could do this with exceptions but there are no exceptions that correspond to the ORA-01847 error for mismatched day and month.
Here is what I tried (the print procedure is a local wrapper for DBMS_OUTPUT.put_line):
PROCEDURE date_check IS
start1 DATE ;
BEGIN
select to_date(nvl(yearcollected,'9999') ||'/'|| nvl(monthcollected,'01') ||'/'|| nvl(daycollected,'01'),'YYYY/MM/DD'))) into start1 from incoming_data where id=1 ;
     BEGIN
          update temp_test set test_date = start1 where id=1 ;
     EXCEPTION
          WHEN OTHERS THEN
          print('Date error message from exception block');
     END;
print('Processing continues after handling date exception') ;
END date_check ;
Is there a way to catch this kind of error and continue processing after logging a message?
-=beeky

Answer 1

Hi, Beeky,
There are lots of different error messages associated with bad dates. Rather than try to catch them all, I use a BEGIN ... EXCEPTION block that contains nothing but a TO_DATE call. This is one of the rare occassions when I think "EXCEPTION WHEN OTHERS" is okay,
The following function comes from a package. If you want to make a stand-alone function, remember to say " *CREATE OR REPLACE* FUNCTION ...".
--          **   t o _ d t   **
--     to_dt attempts to convert in_txt (assumed to
--          be in the format of in_fmt_txt) to a DATE.
--     If the conversion works, to_dt returns the DATE.
--     If the conversion fails for any reason, to_dt returns in_err_dt.
FUNCTION     to_dt
(     in_txt          IN     VARCHAR2                    -- to be converted
,     in_fmt_txt     IN     VARCHAR2     DEFAULT     'DD-MON-YYYY'     -- optional format
,     in_err_dt     IN     DATE          DEFAULT     NULL
RETURN DATE
DETERMINISTIC
AS
BEGIN
     -- Try to convert in_txt to a DATE.  If it works, fine.
     RETURN     TO_DATE (in_txt, in_fmt_txt);
EXCEPTION     -- If TO_DATE caused an error, then this is not a valid DATE: return in_err_dt
     WHEN OTHERS
     THEN
          RETURN in_err_dt;
END     to_dt
;