From: | Waldemar Bergstreiser <littlesuspense(at)web(dot)de> |
---|---|
To: | Greg Stark <gsstark(at)mit(dot)edu> |
Cc: | pgsql-general(at)postgresql(dot)org, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
Subject: | Re: |
Date: | 2009-06-30 11:14:10 |
Message-ID: | 1744923522@web.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
> >> > -- c *= b *= a =* d =* f
> >> > select * from a, outer( b, outer c), outer (d, outer f )
> >> > where a.b_id = b.id and b.c_id = c.id and a.d_id = d.id and d.f_id = f.id;
> >>
> >> from a full join b on (a.id=b.id)
> >> full join c on (b.id=c.id)
> >> full join d
> >>
> >
> > I guess, you don't get it. Probably so
>
> I don't get it either. by *= do you mean the Oracle-style outer join?
> in which case why is this not just
>
> select * from a,
> left outer join b on (a.b_id = b.id)
> left outer join c on (b.c_id = c.id)
> left outer join d on (a.d_id = d.id)
> left outer join f on (d.f_id = f.id)
>
The equal expression would be like this:
select * from a
left outer join (b left outer join c on (b.c_id = c.id) ) on (a.b_id = b.id)
left outer join (d left outer join f on (d.f_id = f.id) ) on (a.d_id = d.id)
and that is a double length of original SQL and has not very clear syntax in my opinion.
Additionally it can be very funny if we try to append a join conditions like "c.iso = d.iso"
> You can parenthesize it different ways but I think the result in this
> case is actually the same.
>
I'm not sure.
> > select * from a left outer join b on (a.b_id=b.id) ....
> >
> > But I don't see any clear way to specify that table C should be outer joined only if we got a row from table B.
>
> Well that would be the default since if you get no row from b b.c_id
> will be null.
>
and if I have a row in table C where c.id is null? A don't know.
I found a good explanation about informix outer joins.
http://savage.net.au/SQL/outer-joins.html
Please take a look at that.
________________________________________________________________
Neu: WEB.DE Doppel-FLAT mit Internet-Flatrate + Telefon-Flatrate
für nur 19,99 Euro/mtl.!* http://produkte.web.de/go/02/
From | Date | Subject | |
---|---|---|---|
Next Message | Nathaniel | 2009-06-30 11:24:07 | Setting up spatial index |
Previous Message | A. Kretschmer | 2009-06-30 10:15:02 | Re: Am I in intransaction or in autocommit mode? |