Re: Problem using Subselect results

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: oheinz(at)stud(dot)fbi(dot)fh-darmstadt(dot)de
Cc: "pgsql-sql(at)postgresql(dot)org" <pgsql-sql(at)postgresql(dot)org>
Subject: Re: Problem using Subselect results
Date: 2003-07-29 15:00:56
Message-ID: 22142.1059490856@sss.pgh.pa.us
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oheinz(at)stud(dot)fbi(dot)fh-darmstadt(dot)de writes:
> But as this data is time sensitive, we introduce some kind of time stamp - a
> serial which is global to all tables. Now, for each record in table 'one' i
> want to see only the corresponding records in tables two, three, etc... that
> were created before 'one.updatenr'

> SELECT * FROM one, two WHERE (one.two_id=two.two_id AND one.updatenr >
> two.updatenr);

> This might match multiple records in tables two (two_id is not a pk, we have
> historic records in this table). Now I want only the most current version
> before one.updatenr. - And that's where I run into trouble.

You might be able to make this work by using SELECT DISTINCT ON. See
the "weather reports" example in the SELECT reference page.

regards, tom lane

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