I tried to use Business Object Mapper to map the table to a business object. I found that I only can select one table. Is it possible that business object can work with more than one tables? For example, a business object can select the fields from three tables.

The business objects will not prevent a user from being able to add new records, remove records or modify records if it is mapped to a view.  The best way to prevent the user modifying the business object would be to handle either the BeforeDelete and BeforeAddNew events and set e.Cancel = True.  Or you could handle the CheckSecurity event and deny the action.