Re: Timestamp to time_t

On Tue, Sep 15, 2009 at 11:02:52AM -0400, Tom Lane wrote:
> David Fetter <david(at)fetter(dot)org> writes:
> > I've looked through SQL:2008 (well, through
> > 6WD2_02_Foundation_2007-12.pdf), and I didn't find anything that
> > implies that the input time zone needs to be retrievable, nor
> > anything that would specify the syntax for doing so.
>
> EXTRACT()?

I see that EXTRACT() can take a time zone as input, but I don't see
anywhere that could distinguish among the following inputs, once
stored, as they have identical representations in UTC:

SELECT
now() AS "West Oakland",
now() AT TIME ZONE 'UTC' AS "Greenwich",
now() AT TIME ZONE 'Asia/Shanghai' AS "Pudong";
West Oakland | Greenwich | Pudong
-------------------------------+----------------------------+----------------------------
2009-09-15 08:27:00.306403-07 | 2009-09-15 15:27:00.306403 | 2009-09-15 23:27:00.306403
(1 row)

The way we store TIMESTAMP WITH TIME ZONE, the database converts to
UTC, discarding the input time zone in the process. SQL:2008 appears
to allow this, and doesn't appear to have a way to retrieve that input
time zone once a TIMESTAMP WITH TIME ZONE field has been stored.

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david(dot)fetter(at)gmail(dot)com

Remember to vote!
Consider donating to Postgres: http://www.postgresql.org/about/donate