From: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
---|---|
To: | Patrick Welche <prlw1(at)newn(dot)cam(dot)ac(dot)uk> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: null answer - how? |
Date: | 2001-09-19 18:34:56 |
Message-ID: | Pine.BSF.4.21.0109191130380.68729-100000@megazone23.bigpanda.com |
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Thread: | |
Lists: | pgsql-general |
On Wed, 19 Sep 2001, Patrick Welche wrote:
> select coalesce(sum(deltafromoctets),0)
> from trans,stats
> where stats_id=stats.id
> and (timeslicet < '1:05' OR timeslicet > '6:05')
>
> returns a number (9188191930), whereas
>
> select coalesce(sum(deltafromoctets),0)
> from trans,stats
> where stats_id=stats.id
> and (timeslicet < '1:05' OR timeslicet > '6:05')
> and timesliced < '01-May-2001'
>
> prints 0 (or null without the coalesce) as does
>
> select coalesce(sum(deltafromoctets),0)
> from trans,stats
> where stats_id=stats.id
> and timesliced < '01-May-2001'
>
> How can this be?
>
> select * from stats where timesliced is null or timeslicet is null
> select * from trans where deltafromoctets is null
>
> both retun 0 rows.
Are there no rows with timesliced<'01-May-2001'? I think in that
case sum() gives you one row with NULL.
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