Re: 3 way outer join dilemma - Mailing list pgsql-general

On Tue, 2003-08-19 at 11:13, terry@ashtonwoodshomes.com wrote:
> Uh, sorry.  Explicitly stating t1.fid = X and t2.vid = Y was to imply that,
> but a better example would be:
>
> SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
> FROM t1, t2, t3
> WHERE t1.fid = X
>   AND t2.vid = Y
>   AND t1.id = t2.id
>   AND t3.fid = t1.fid
>   AND t3.vid = t2.vid
>
> Now, I discover that the record in t3 may not always exist,
> so somehow I want to do an outer join...
>
> SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
> FROM t1, t2, OUTER JOIN t3 ON (t3.fid = t1.fid AND t3.vid = t2.vid)
> WHERE t1.fid = X
>   AND t2.vid = Y
>   AND t1.id = t2.id

How about:
SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
FROM (t1 join t2 on t1.id = t2.id)
      LEFT OUTER JOIN t3 on (t3.fid = t1.fid AND t3.vid = t2.vid)
WHERE t1.fid = X
  AND t2.vid = Y
;

> Thanks
>
> Terry Fielder
> Manager Software Development and Deployment
> Great Gulf Homes / Ashton Woods Homes
> terry@greatgulfhomes.com
> Fax: (416) 441-9085
>
>
> > -----Original Message-----
> > From: pgsql-general-owner@postgresql.org
> > [mailto:pgsql-general-owner@postgresql.org]On Behalf Of scott.marlowe
> > Sent: Tuesday, August 19, 2003 11:55 AM
> > To: terry@ashtonwoodshomes.com
> > Cc: Postgres (E-mail)
> > Subject: Re: [GENERAL] 3 way outer join dilemma
> >
> >
> > On Mon, 18 Aug 2003 terry@ashtonwoodshomes.com wrote:
> >
> > > Here's what I have (simplified)
> > >
> > > SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
> > > FROM t1, t2, t3
> > > WHERE t1.fid = X
> > >   AND t2.vid = Y
> > >   AND t3.fid = t1.fid
> > >   AND t3.vid = t2.vid
> > >
> > > Now, I discover that the record in t3 may not always exist,
> > so somehow I
> > > want to do an outer join...
> > >
> > > SELECT t1.fid, t1.t1_data, t2.vid, t2.t2_data, t3.t3_data
> > > FROM t1, t2, OUTER JOIN t3 ON (t3.fid = t1.fid AND t3.vid = t2.vid)
> > > WHERE t1.fid = X
> > >   AND t2.vid = Y
> > >
> > > But I get the statement that "t1 is not part of JOIN"
> >
> > If t3 may not have a record, then how can you be using it to join t2 ?
> >
> > It seems that if t3 doesn't exist, then of course "AND t3.vid
> > = t2.vid" is
> > going to be "AND NULL = t2.vid" which of course, will always
> > be false,
> > i.e. you'll never be able to join t2.  Is there a common key
> > between t2
> > and t1?

--
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Ron Johnson, Jr. ron.l.johnson@cox.net
Jefferson, LA USA

"Man, I'm pretty. Hoo Hah!"
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