Sam Mason <sam@samason.me.uk> wrote:
>> > any definition of "division" I've ever been able to think of [is]
>> > ill defined
>> Yep, you would probably need some safety margin and add a
>> "WHERE" clause. I should have thought about that earlier as
>> I recently stumbled (again) over why "INTERVAL / INTERVAL"
>> was not defined.
> Not sure what you mean by a "safety margin", but I don't think it would
> help much. Hours are defined using seconds (they're *always* 3600
> seconds long, but, say, a day isn't *always* 24 hours long) so I don't
> see what a safety margin would do.
A month can last 28 to 31 days and a year 365 to 366 days,
but for example:
| tim=# SELECT EXTRACT('epoch' FROM '1 month'::INTERVAL) / 60.0 / 60 / 24;
| ?column?
| ----------
| 30
| (1 Zeile)
| tim=#
You would have to adjust the result of "(EXTRACT('epoch'
FROM B) - EXTRACT('epoch' FROM A)) / EXTRACT('epoch' FROM
C)" by a factor of 31/30 (30/28? 28/30?) and then chop off
timestamps after B with a "WHERE" clause.
JFTR: Hours can of course also be 3601 (or theoretically
3599) seconds long, but not in PostgreSQL :-).
Tim
