How to find all disconnected graphs in a node/edge sql representation?

How to find all disconnected graphs in a node/edge sql representation?

Given a given nodes and edges tables, how to find all disconnected graphs
using TSQL?
References :
http://techportal.inviqa.com/2009/09/07/graphs-in-the-database-sql-meets-social-networks/
http://apps.cytoscape.org/apps/subnetworkcreator