How to code custom entity to access more than one database table? I have an entity that uses two tables, when I describe it in hook_entity_info() as far as I know I can only tell it about the base table. The base table is subscriber, I also have a table disease_catagories which stores the results of a select list. (stores the subscriber id, and the taxonomy term id. It can store any number of items with the same subscriber id and different taxonomy term ids)

I need the entity to contain an array of those taxonomy term ids, but I don't know how to connect that database table with the base table. are there any good articles that discuss how to attach a second table to the entity (maybe as field data)?
Entity API itself can only interact with one base table for joining to fields, querying with EntityFieldQuery, loading/saving revisions, etc, but you can use more than one table for storage if you implement your own storage controller which you can specify in your hook_entity_info().

You'll want to subclass DrupalDefaultEntityController and override the load() method and buildQuery() method if you want some EntityFieldQUery support.

If you are using Entity API module, you'll want to extend EntityAPIController and override the save(), load(), and delete() methods for full CRUD support.