Strange invalid month error.

Question

Hi all,
I have a function which receives a date and then returns a text string saying what day of the week it is, ie Monday Tuesday etc etc
For example sakes I'll say the function is called dayoftheweek and we use the function like 'select somedate, dayoftheweek(somedate) from dual'
Now, the bit within the function that works out the day is as below
SELECT TO_CHAR(TO_DATE(p_date, 'DD/MM/RRRR') ,'DAY') from dual (p_date is the internal function variable for the date passed in.)
Now, if I do this
select dayoftheweek('25-MAY-09') from dual -- this works.
But...
select dayoftheweek('25/05/09') from dual -- this does not work, I get an ora 01843 invalid month error.
So, I assumed it was something to do with the logic that worked out the day of the week.
However, the below works.
SELECT TO_CHAR(TO_DATE('25/05/09', 'DD/MM/RRRR') ,'DAY') from dual
Does anyone know why when passing a date to the function in format 'select dayoftheweek('25/05/09') from dual' does not work but if I use this format within the function logic as above it does work?
Cheers,
rg

Answer 1

Hello,
Oracle does not know your date format:
select dayoftheweek('25/05/09')I.e, it does not know that the date you are passing in is in the form of 'DD/MM/MM'. You must tell it (since it isn't your default format):
select dayoftheweek(to_date('25/05/09', 'DD/MM/YY'))If all you wanted, however, was the day of the week from a date, then:
TO_CHAR(to_date('25/05/09', 'DD/MM/YY'), 'DAY')Will give you that.
And by the way, this:
SELECT TO_CHAR(TO_DATE('25/05/09', 'DD/MM/RRRR') ,'DAY') from dualIs correct by chance, even though you're getting no error you may get the wrong result, because you're telling oracle you're passing in 4 digits for the year, yet you're only passing in two.
Edit Beware:
SQL> SELECT TO_CHAR(TO_DATE('25/05/09', 'DD/MM/RRRR'), 'YYYY') from dual;
TO_C
2009
SQL> SELECT TO_CHAR(TO_DATE('25/05/09', 'DD/MM/YYYY'), 'YYYY') from dual;
TO_C
0009