Hi. I am looking for a way to write a SELECT that finds connectivity components of a graph or at least for one that given two nodes determines if there is a path between them. It seems that this is not possible, no matter what graph representation I choose. Which constructs from set theory are missing in SQL? Set of all subsets is one I am missing, or can it be done somehow? Is anybody else thinking about the limits of SQL? As often I am probably not the first to ask these questions. Any pointers? Sincerely, Joachim ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org