Re: Problem in age on a dates interval

From: "Alexander M(dot) Pravking" Luis Sousa Tom Lane ,Theodore Petrosky , pgsql-sql(at)postgresql(dot)org Re: Problem in age on a dates interval 2004-07-19 10:46:46 20040719104646.GH81997@dyatel.antar.bryansk.ru (view raw, whole thread or download thread mbox) 2004-07-16 08:45:24 from Luis Sousa  2004-07-16 11:52:14 from Theodore Petrosky   2004-07-16 14:34:07 from Tom Lane    2004-07-19 09:00:50 from Luis Sousa     2004-07-19 10:46:46 from "Alexander M(dot) Pravking"      2004-07-20 08:17:15 from Luis Sousa pgsql-sql
```On Mon, Jul 19, 2004 at 10:00:50AM +0100, Luis Sousa wrote:
> I worked around this problem returning the difference between the two
> dates, using extract doy from both.
> Anyway, this will cause a bug on my code when changing the year. Any ideas?

Why don't you use the minus operator?

SELECT '2004-05-14 16:00'::timestamp - '2004-02-18 16:00'::timestamp;
?column?
----------
86 days

Or, if you need the age just in days:

SELECT extract(day from '2004-05-14 16:00'::timestamp - '2004-02-18 16:00'::timestamp);
date_part
-----------
86

or

SELECT '2004-05-14 16:00'::date - '2004-02-18 16:00'::date;
?column?
----------
86

Note that '2004-05-14 16:00'::date is actually '2004-05-14 00:00'::date,
so the last two are not always equal.

> Tom Lane wrote:
>
> >Theodore Petrosky <tedpet5(at)yahoo(dot)com> writes:
> >
> >
> >>wow.... at first I thought I had my head around a leap
> >>
> >>
> >
> >I think what's going on here is a difference of interpretation about
> >whether an "M months D days" interval means to add the months first
> >or the days first.  For instance
> >
> >2005-02-18 plus 2 months = 2005-04-18, plus 24 days = 2005-05-12
> >
> >2005-02-18 plus 24 days = 2005-03-14, plus 2 months = 2005-05-14
> >
> >The timestamp-plus-interval operator is evidently doing addition the
> >first way, but it looks like age() is calculating the difference in a
> >way that implicitly corresponds to the second way.
> >
> >I have some vague recollection that this has come up before, but
> >I don't recall whether we concluded that age() needs to be changed
> >or not.  In any case it's not risen to the top of anyone's to-do list,
> >because I see that age() still acts this way in CVS tip.
> >
> >			regards, tom lane

--
Fduch M. Pravking

```

pgsql-sql by date

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