SchemaSpy is a Java-based tool (requires Java 5 or higher) that
analyzes the metadata of a schema in a database and generates a visual
representation of it in a browser-displayable format. It lets you click
through the hierarchy of database tables via child and parent table
relationships as represented by both HTML links and entity-relationship
diagrams. It's also designed to help resolve the obtuse errors that a
database sometimes gives related to failures due to constraints.