CDBcriteria for heirarchical relation

I have a model Organization that is heirarchical; for example, there’s a College of Social Sciences, and in it a number of Schools - School of Advertising, School of Journalism, etc. - and then within each school there are some departments - the School of Advertising has a Department of Public Relations, a Department of Merchandising, etc.

In the DB, each Organization has fields id, name, and parent_id.

I also have a model Student, with a MANY_MANY relationship between Student and Organization. Is there a way I can filter a CGridView in the Student model by organization so that if I pick the "College of Social Sciences" from the dropdown, it also displays students who belong to a child organization of the one chosen in the dropdown? That is to say, so that if I filter by College of Social Sciences, it shows me Students in the School of Advertising or the Department of Public relations?

bump…anyone have any ideas?