Ben Reece wrote:
I think this is the proper functionality. The middle 4 queries are
trying to subtract 6 months from:
2007-08-31
2007-08-30
2007-08-29
2007-08-28
Since 6 months prior to Aug is Feb, and the last day of Feb is the
28th, it makes sense to me that Feb 28 would be six months prior to
Aug 31. The alternative seems to be some time in early March, but
that would only be 5 months previous, which makes no sense.
You get the same result if you try to go to a month with only 30 days
-- DATE_SUB( DATE_SUB(CURDATE(), INTERVAL 45 DAY), INTERVAL 2 MONTH)
will return 2007-06-30, so I don't think it has anything to do with a
February/leap year problem.
Ben
Jennifer Charrey wrote:
This is expected behavior and you can find it in the MySQL documentation:
> If you add MONTH, YEAR_MONTH, or YEAR and the resulting date has a
day that is larger than the maximum day for the new month, the day is
adjusted to the maximum days in the new month:
>
> mysql> SELECT DATE_ADD('1998-01-30', INTERVAL 1 MONTH);
> -> '1998-02-28'
http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_date-add
As Ben said, a different answer probably wouldn't even make sense.
March 3 would not be 6 months ago.
Yeah, further digging on the mysql developers site gave me this reply as
well. I guess I will need to flesh something out that will handle that
scenario because you are right, it does kind-of make sense.
thnx,
-jim
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