> -----Ursprüngliche Nachricht----- > Von: "Scott Marlowe" <scott.marlowe@xxxxxxxxx> > Gesendet: 30.06.09 10:17:11 > An: Waldemar Bergstreiser <littlesuspense@xxxxxx> > CC: pgsql-general@xxxxxxxxxxxxxx > Betreff: Re: > On Tue, Jun 30, 2009 at 2:00 AM, Waldemar > Bergstreiser<littlesuspense@xxxxxx> wrote: > >> On Mon, Jun 29, 2009 at 2:08 PM, littlesuspense<littlesuspense@xxxxxx> wrote: > >> > Hi Volk, > >> > > >> Note that the word outer is just noise in pgsql, i.e. it's not needed. > >> What you've got are left outer, right outer, and full outer joins. > >> All can be called just left, right, or full joins. Note that inner > >> joins are just called joins. > >> > >> > select * from a, outer b where a.id = b.id; > >> > >> select * from a full join b on (a.id=b.id) where ... > >> select * from a left join b on (a.id=b.id) where ... > >> select * from a join b on (a.id=b.id) where ... > > > > this is only a simple case, but outer can make syntax more clean in complicated joins. > > Just try to rewrite query below with left outter joins. I had not found any compact syntax. > > > > -- 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 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. > and so on. Doesn't seem any lestt compact or readable to me. > >> What you get with postgresql is mostly ANSI standard stuff, which > >> left/right/full outer and inner joins are. > >> > > And I like that, but each SQL RDMS system and each SQL dialect de facto provide also a lot of standard extensions. So the RDMS user has a choice, to use such extensions or not. And I think postgres can only win if we it have more and very sane extensions. > > If the standard SQL syntax does the job, I see no reason to include > non-standard syntax from other dbs unless they're obviously cleaner > and simpler, and I really don't see that here. Every thing you add to > the query planner / executor costs something in planning and / or > execution times. I am fully agreed with you. My point is, that the syntax with outer is much clearer and can't be so easy rewritten in standard ANSI SQL. And I hope this can be implemented in SQL parser so the planner is not affected, and on the other side, the reduction of overall SQL statement's length can have a positive impact on network traffic and speed of SQL parsing. > > Further, most database engines now support sql standard join syntax, > so there's no great reason to support it for compatibility reasons. > This suggestion is not caused by compatibility consideration. It's just a try to take over a good things from oldies RDMS. ______________________________________________________ GRATIS für alle WEB.DE-Nutzer: Die maxdome Movie-FLAT! Jetzt freischalten unter http://movieflat.web.de -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
