Robert Citek wrote: > On Sun, Jan 10, 2010 at 8:06 PM, Dan Bishop <danbisho...@gmail.com> wrote: >> Robert Citek wrote: >>> Does anyone have any recommendations for books or other resources that >>> deal with working with graphs (i.e. vertexes and edges) using sql? >>> >> I don't think that SQL is the best language for working with graphs, but: >> >> CREATE TABLE Graph ( >> NodeFrom INTEGER, >> NodeTo INTEGER >> ); > > Yes, the Koenigsberg bridge problem is just one example of what I am > referring to. > > I was working on creating a more general model initially with just two > tables: one for vertexes and one for edges, which is a pairing of > vertexes. For example: > > create table vertexes ( vertex integer ) ; > create table edges ( v1 integer, v2 integer ) ; > BEGIN; > INSERT INTO vertexes VALUES (1); > INSERT INTO vertexes VALUES (2); > INSERT INTO vertexes VALUES (3); > INSERT INTO vertexes VALUES (4); > COMMIT;
I store all the data for my waterways route planner in SQLite, but I load it into memory for running Dijkstra's algorithm on it to find the shortest (when weighted) paths. It's at canalplan.eu if anyone wants a play. One problem you rapidly run into when storing graphs in SQL, in my limited and non-expert experience, is that - as in this example - you end up with edge records each of which refers to two vertices. My database maintenance and update code is riddled with: SELECT ... FROM link WHERE place1=x AND place2=y OR place1=y AND place2=x; and similar. Apart from imposing a condition (such as always having v1 < v2 in the example code) is there any sensible way round this? _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
