From: Mark Fenbers <Mark.Fenbers@noaa.gov>
To: chester c young <chestercyoung@yahoo.com>
Cc: PostgreSQL - SQL <pgsql-sql@postgresql.org>
Subject: Re: group by complications
Date: Thu, 16 Feb 2006 12:47:55 -0500
Message-ID: <43F4BACB.60600@noaa.gov> (raw)
In-Reply-To: <20060214022937.77875.qmail@web54305.mail.yahoo.com>
References: <20060214022937.77875.qmail@web54305.mail.yahoo.com>
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Wow! I didn't know you could have a (select ...) as a replacement for
a 'from' table/query. Your SQL worked as-is, except I had to add a
'limit 1' to the first subquery.<br>
<br>
Thanks! I would have never figured that out on my own!<br>
<br>
Mark<br>
<br>
chester c young wrote:
<blockquote cite="mid20060214022937.77875.qmail@web54305.mail.yahoo.com"
type="cite">
<pre wrap="">--- Mark Fenbers <a class="moz-txt-link-rfc2396E" href="mailto:Mark.Fenbers@noaa.gov"><Mark.Fenbers@noaa.gov></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">select l.lid,l.fs,max(h.obstime) from location as l
inner join height as h on h.lid = l.lid
where l.fs > 0.0
group by l.lid,l.fs;
The above query works as expected in that is fetches the lid, fs and
time of the latest observation in the height table (for the
corresponding lid), but I also want to fetch (i.e., add to the select
list) the corresponding reading (h.obsvalue) which occurs at
max(h.obstime). I'm having trouble formulating the correct SQL
syntax
to pull out the l.lid, l.fs, and the most recent h.obvalue (with or
without the time that it occurred).
Logistically, I want to do something like this:
select l.lid,l.fs,most_recent(h.obsvalue) from location as l
inner join height as h on h.lid = l.lid
where l.fs > 0.0
group by l.lid,l.fs;
</pre>
</blockquote>
<pre wrap=""><!---->
use your original query as part of the from clause, then add columns to
it through a subquery or a join. try something like this:
select q1.*,
(select obsvalue from height where lid=q1.lid and obstime=q1.obstime)
as obsvalue
from
(select l.lid,l.fs,max(h.obstime) as obstime1 from location as l
inner join height as h on h.lid = l.lid
where l.fs > 0.0
group by l.lid,l.fs ) q1;
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</pre>
</blockquote>
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To: pgsql-sql@postgresql.org
Cc: Mark.Fenbers@noaa.gov, chestercyoung@yahoo.com
Subject: Re: group by complications
In-Reply-To: <43F4BACB.60600@noaa.gov>
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