Sql gurus help needed.. simple but awkward

Question

Im trying to use dates stored in a char field...field called segment1
2006/09/11 00:00:00 This is the format they are being stored as
When i select this data im converting to date format to make it look good to_date(tppc.segment1,'YYYY-MM-dd:HH24:MI:SS')
The problem is in the where clause, when i goto put a condition in its like it does not recognise the date format.....
so where to_date(tppc.segment1,'YYYY-MM-dd:HH24:MI:SS') = '31-OCT-2008' ..... error - ORA-01841: (full) year must be between -4713 and +9999
so where to_date(to_date(tppc.segment1,'YYYY-MM-dd:HH24:MI:SS'),'DD-MON-YYYY') = '31-OCT-2008' again error ORA-01841
I have checked all the data and the format 2006/09/11 00:00:00 is the same in all records...
Does someone know what to do ....
Data Output ---- TO_CHAR(to_date(tppc.segment1,'YYYY-MM-dd:HH24:MI:SS'),'DD-MON-YYYY') - 11-SEP-2006

Answer 1

Hi Sharky,
Are you completely sure that all of the records in your table contain properly formated date strings in segment1?
you can check it with a simple function:
create or replace FUNCTION "VALIDATE_DATE"
    (   date_String VARCHAR2,
        format      VARCHAR2 := 'dd-mon-yyyy' )
    RETURN VARCHAR2
    DETERMINISTIC
IS
    dt DATE;
BEGIN
    dt := to_date( date_string, format );
    RETURN 'Y';
EXCEPTION
    WHEN OTHERS THEN
        RETURN 'N';
END;
/which you use to select records which have invalid dates like so:
select *
  from your_table
where validate_date(segment1, 'YYYY-MM-dd:HH24:MI:SS')='N';The next thing to consider is that when you use a to_date function on segment1 you are converting it to a date data type, but in your comparisson you are comparing that data data type to a string constant. To perform the equality test Oracle needs to change the data type of one side of the equality to match the data type on the other side of the equality. Generally speaking you should explicitly convert one of them to match the other. For example you should wrap your string constant in a to_date function so you end up comparing two dates, or since the segment1 value is already in a canonical date format, you could change your string constant to the same canonical date format removing the to_date off of segement1 so you are just doing a string comparison.