Hi What are the best practices for subclassing entities in relational databases?
The most efficient/fastest way is to use one table for all subclasses. But sometimes this is not very... err... nice. Especially for nicely complex hierarchy. In the OOP world Everything(tm) can descend from the Object class. But then do you just create one "objects" table and then expect every entity to be there? I'm currently developing a database system with only two entities, Persons and Topics (things attached to persons, like their e-mail addresses, books read, movies liked, basically anything and nothing in general, etc.) Actually persons are also topics in the proper sense of hierarchy (just like the Topic Map model -- http://www.topicmap.org), but when converted to relational it gets messy. The thing is I also need to add associations between these entities. And so I have to have relationship entities (person-to-person relationship), association entities (person-to-topic relationship), and yet another association entities (topic-to-topic relationship). In the OOP world I would only need two base classes (topics and associations), but in the relational world this gets transformed to 5 entities, and more for the many-to-many join tables (i.e. a association entity has a association types table and a association many-to-many table). I would appreciate any suggestions. -- Hendy Irawan http://www.gauldong.net http://dev.gauldong.net -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php