Message-ID: <4F4EB305.7010409@iinet.net.au>
Date: Thu, 01 Mar 2012 10:21:41 +1100
From: Peter Faulks <faulksp@iinet.net.au>
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To: "pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
Subject: Re: date arithmetic with columns
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Bit more googling and I came up with:

r.utc + CAST( tz.diffmins || ' ' || 'minutes' AS interval)

It works, but is it the best way?

On 1/03/2012 6:50 AM, Peter Faulks wrote:
> I have two columns in two distinct tables, one is the starting time of
> an event, timestamp without time zone. Data is the utc datetime (for
> sorting across time zones), the other is the number of minutes to add.
>
> I am migrating from Firebird. One of the queries uses the dateadd
> function to build a local starting time thus:
>
> SELECT CAST(DATEADD(tz.diffmins MINUTE TO r.utc) AS TIME) AS ts
> FROM races r JOIN tracks t ON t.trk = r.trk
> JOIN timezones tz on tz.state = t.state....
>
> The equivalent postgres would be along the lines of
>
> SELECT r.utc + INTERVAL '480 minutes'
>
> How can I substitute the hard-coded 480 for the tz.diffmins?
>