Thanks, that looks useful. I'll investigate once I've got the servers upgraded
and replication running.
Bruno Wolff III wrote:
>
> On Wed, Jul 13, 2005 at 18:15:12 +0000,
> markMLl.pgsql-general@telemetry.co.uk wrote:
> > Many thanks Tom. Inconvenient from the point of view of the application
> > but still useful information.
> >
> > The situation is that I've got a query with numerous subselects, each of
> > which has to return exactly one row so I was doing a union with a nulled
> > record then selecting the most recent: obviously I need to see bona-fide
> > data if it's there.
>
> you can order by datecol is null, datecol desc to get the most recent
> non null date. For example:
> area=> select day from (select 'today'::date as day union select
> 'tomorrow'::date as day union select null as day) as un order by day is null,
> day desc;
> day
> ------------
> 2005-07-16
> 2005-07-15
>
> (3 rows)
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]