ERDs or entity relationship diagrams are a fundamental element in database design. ERDs are a visual method of showing how different fields in a database relate to each other. One of the main goals in database design is to only capture information once. This is more easily done when the database is fully documented. For a quick tutorial on ERDs visit
. http://folkworm.ceri.memphis.edu/ew/SCHEMA_DOC/comparison/erd.htm.