Joe Celko models graphs using ANSI SQL:
The initial proposed solutions to construct the subgraphs were essentially procedural traversal, dumping pairs of nodes into a temp table and incrementing a counter.
Let us try getting out of a procedural mindset and starting to think in sets instead. Let us give each subgraph a name, and a member node. Essentially, this directly models. The diagram I just gave you a paragraph or two ago. The next question is how do we get names for the subgraphs. I will propose the simple solution that each subgraph takes the name of the lowest element in it. This would give us a table that looks like this:
Read the whole thing. Given the recent revival of graph databases, it’s important to take note that you can model the network-style problems using either graphs or relations; the trick is figuring out which is going to give you better long-run performance.