Date Comparison Issue

Question

Hi,
This might come as a dumb question, but i'm having issues comparing dates using to_date() function.
One of the table has a VARCHAR column which has values in the format '01-JAN-2009'
i'm trying to convert it to a date using to_date(field_value) and compare it to a hard coded date.
I get ORA 01858 error.
I can however convert that field in a select statement and not get any error.
My Query is as follows,
SELECT
o.option_descr, to_date(o.field_value) as converted_date,
o.field_value as raw_value_from_db--- same as comparison expression
FROM REP_GROUP G
JOIN
REP_REPORT R ON r.report_id = G.report_id
JOIN
REP_OPTION O ON O.GROUP_ID = G.GROUP_ID
WHERE r.report_name = 'ABCD'
and
to_date(o.field_value) <= to_date('01-APR-2009')
AND group_descr = 'Quarter'
-- ORDER BY TO_DATE(O.FIELD_VALUE) DESC;
I tried by providing the date mask as well ....

Answer 1

Hi,
user7306711 wrote:
I tried by providing the date mask as well ....Good! You should always pass the 2nd argument, the date mask, whenever you use TO_DATE.
The problem may be that there is invalid data in o.field_value on one of the rows that is being rejected beacuse of r.report_name or groupd_descr.
It may help to re-write the WHERE clause to guarantee that the test for o.field_value will be done last:
WHERE     CASE
          WHEN  r.report_name     != 'ABCD'
          THEN  0
          WHEN  group_descr     != 'Quarter'
          WHEN  TO_DATE (o.field_value, 'DD-MON-YYYY') > DATE '2009-04-01'
          THEN  0
          ELSE  1
     END  = 1Or you can use a no-fail version of TO_DATE, like the one below. It will be slower, but if that's the only price you have to pay for storing your dates in a VARCHAR2 column, you're very lucky.
CREATE OR REPLACE 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
--     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.
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
;