Question

I’m using this sql query:

select sysdate, sysdate - INTERVAL '6' month from dual;

But it is return: ORA-01839: date not valid for month specified.

Which is weird, because if I change the the number into 9, it is return the date (sysdate = 31/05/11 and the subtracted is 31/08/10). I’m also tried using different value: 1,3,6,8,11 also not working, but 2,4,5,7,9,12 are working.

From the numbers, I think it is because the resulting quert doesn’t have 31 days for that month. Is this the expected behavior? Because in MySQL, I can use the query (select now() – Interval 6 Month;) to get the correct value. Is there any other way?

I am using Oracle 11.1.0.6

Answer 1

select sysdate,add_months(sysdate,-6) from dual;