Re: 3 way outer join dilemma

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

Thanks

Terry Fielder
Manager Software Development and Deployment
Great Gulf Homes / Ashton Woods Homes
terry(at)greatgulfhomes(dot)com
Fax: (416) 441-9085

> -----Original Message-----
> From: pgsql-general-owner(at)postgresql(dot)org
> [mailto:pgsql-general-owner(at)postgresql(dot)org]On Behalf Of scott.marlowe
> Sent: Tuesday, August 19, 2003 11:55 AM
> To: terry(at)ashtonwoodshomes(dot)com
> Cc: Postgres (E-mail)
> Subject: Re: [GENERAL] 3 way outer join dilemma
>
>
> On Mon, 18 Aug 2003 terry(at)ashtonwoodshomes(dot)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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