To: "Raman" <ramang@smartdatainc.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Query TIME ZONE 
In-reply-to: <003c01c3e55e$54b12d50$d4c7a8c0@raman> 
References: <003c01c3e55e$54b12d50$d4c7a8c0@raman>
Comments: In-reply-to "Raman" <ramang@smartdatainc.com>
	message dated "Wed, 28 Jan 2004 10:49:37 +0530"
Date: Wed, 28 Jan 2004 00:58:32 -0500
Message-ID: <8028.1075269512@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

"Raman" <ramang@smartdatainc.com> writes:
> [ okay: ]
> "select current_time AT TIME ZONE INTERVAL '+5:30'"
> [ not okay: ]
> "select current_time AT TIME ZONE INTERVAL time_difference from customer_events"

"TIME ZONE INTERVAL" is not a SQL construct.  You have misunderstood the
interaction of two different SQL constructs:
	timestamp AT TIME ZONE timezonespec
	INTERVAL 'interval-literal'
One of the possible forms of "timezonespec" in the AT TIME ZONE operator
is an interval value, so your first example works fine.  Your second
example does not work because the INTERVAL 'foo' construct is only for
simple literal constants.

> here : time_difference - is my varchar column in the table customer_events.

Why are you using varchar rather than an interval column?  An interval
value would work directly in this construct and would provide some
checking that entered values are sane.

If you are absolutely intent on using varchar as the column datatype,
you can do a run-time cast like this:
	select current_time AT TIME ZONE "interval"(time_difference) from customer_events
but don't complain when the query fails because some rows contain
time_difference strings that don't look like legal interval values...

			regards, tom lane