Question

Do you know any reference where to find SQL queries for traversing trees/graphs?

I found this one: http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html and Celko’s book.

Problem is that the majority of resources I found refers to adiacency model trees, I’m using a normal edge list model.

Eg. queries or procedures to extract subpaths, subtrees, etc.

Thanks

Answer 1

Nested sets models are best for hierarchical aggregations. Traversals for general graphs are best done with the adjacency list model. But I have used nested sets for convergent graphs by splitting nodes

 A
/ \
B C
\ /
 D

Becomes

 A
/ \
B C
|  |  
D  D

Since nests sets keep nodes in a separate table, this is easy.

You can also do a general graph as a forest of all possible spanning trees