On Sat, Jun 04, 2005 at 21:53:24 +0200, Joachim Zobel <jzobel@xxxxxxxxxxxxxxx> wrote: > Am Samstag, den 04.06.2005, 07:38 -0500 schrieb Bruno Wolff III: > > On Sat, Jun 04, 2005 at 11:31:02 +0200, > > Joachim Zobel <jzobel@xxxxxxxxxxxxxxx> wrote: > > > > > > ... And it seems that > > > a plain SELECT that tells me if a path exists is not possible... > > > > When 'WITH' gets implemented then you should be able to do this. I think > > there was some recent talk about that, but I don't know if it is going to > > make it in to 8.1. We'll know in about a month though. > > So WITH will allow recursion so I can walk the graph, right? Does this > mean I can recursively join until a terminating condition is reached? It can be used to compute transitive closures, which I think is what you are really looking for. If you look at the TODO page (http://www.postgresql.org/docs/faqs.TODO.html) you will see two entries for WITH under Exotic Features: Add SQL99 WITH clause to SELECT Add SQL99 WITH RECURSIVE to SELECT There is a short example of this on pages 439-440 of "SQL for Smarties" second edition. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
