> Wow, that is a weird case. In the first test, we count the number of
> days because it is less than a full month. In the second case, we call
> it a full month, but then forget how long it is. Not sure how we could
> improve this.
I do not think this needs to be improved, the problem is given two
dates you can substract them in three different ways,
1.- (year months)+(days)+(hours minutes seconds), which is what age
does and is documented as such.
folarte=# select age('2013-11-24 16:41:31','2012-10-23 15:56:10');
age
-----------------------------
1 year 1 mon 1 day 00:45:21
(1 row)
Which is apropiate for things like 'I'm xxx old'
2.- (days)+(hours-minutes-seconds), which is what substractint dates
do ( or seems to do for me, as I've done:
select timestamp '2013-11-23 16:41:31' - '2012-10-23 15:56:10';
?column?
-------------------
396 days 00:45:21
Which I can not find a use for, but there sure are and I'm doomed to
find one soon.
3.- Exact duration ( I do this a lot at work as I need to calculate
call durations ):
folarte=# select extract(epoch from timestamp '2013-11-23 16:41:31') -
extract(epoch from timestamp '2012-10-23 15:56:10');
?column?
----------
34217121
(1 row)
folarte=# select (extract(epoch from timestamp '2013-11-23 16:41:31')
- extract(epoch from timestamp '2012-10-23 15:56:10')) * interval '1
second';
?column?
------------
9504:45:21
(1 row)
The problem I see is intervals are really complicated and difficult to
undestand, so it is at most a documentation problem ( people usually
understimate the difficulty of working with them, I see this a lot at
work ).
Francisco Olarte.