From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: ww zz <ts_999@yahoo.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: how to do this query?
Date: Tue, 20 May 2003 09:46:37 -0700 (PDT)
Message-ID: <20030520094321.T68048-100000@megazone23.bigpanda.com> (raw)
In-Reply-To: <20030520160011.81254.qmail@web41803.mail.yahoo.com>
On Tue, 20 May 2003, ww zz wrote:
> New to sql and may be a simple question for you:
>
> I have four tables
>
> sample: sid, sname
> make: sid, mdate
> measure: sid, mdate, rid
> result: rid, resultdata
>
> for a gaven sample it always has a sid and sname, but
> it may or may not have any entries in the other
> tables, the sample could be measured more than once
> and each measure give a result row.
> question:
> how do I do a query that given a sid, it will retrieve
> all the information available in the four tables, if
> there are available. If, for example, all tables have
> some entry for a gave sample it will retreve all the
> information, if the "measure" and "result" are empty
> for that sample it will give only the 'sample' and
> 'make' information....
Well, you're not going to get a limited column set, but you can
get NULLs in the non-applicable table columns by using outer joins.
Maybe something like something like
select * from
sample left outer join make using (sid)
left outer join measure using (sid)
left outer join result using (rid)
where sid=<value>;
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To: pgsql-sql@postgresql.org
Cc: sszabo@megazone23.bigpanda.com, ts_999@yahoo.com
Subject: Re: how to do this query?
In-Reply-To: <20030520094321.T68048-100000@megazone23.bigpanda.com>
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