Hi, As far as I know SQL Server has some similar feature. It does not join if not necessary, more exactly: if the result would be the same if it joined the table. Here is another example: http://www.ianywhere.com/developer/product_manuals/sqlanywhere/0902/en/html/dbugen9/00000468.htm This would be a fantastic feature. Best Regards, Otto 2006/1/12, Alessandro Baretta <a.baretta@xxxxxxxxxxxxxxx>: > Ottó Havasvölgyi wrote: > > Hi all, > > > > Is PostgreSQL able to throw unnecessary joins? > > For example I have two tables, and I join then with their primary keys, > > say type of bigint . In this case if I don't reference to one of the > > tables anywhere except the join condition, then the join can be eliminated. > > Or if I do a "table1 left join table2 (table1.referer=table2.id)" (N : > > 1 relationship), and I don't reference table2 anywhere else, then it is > > unnecessary. > > It cannot possibly remove "unnecessary joins", simply because the join > influences whether a tuple in the referenced table gets selected and how many times. > > Alex > > > -- > ********************************************************************* > http://www.barettadeit.com/ > Baretta DE&IT > A division of Baretta SRL > > tel. +39 02 370 111 55 > fax. +39 02 370 111 54 > > Our technology: > > The Application System/Xcaml (AS/Xcaml) > <http://www.asxcaml.org/> > > The FreerP Project > <http://www.freerp.org/> >
