postgresql7.1 select distinct callback, callback_type from subsite_callbacks where object_type in (select t2.object_type from acs_object_types t1, acs_object_types t2 where t2.tree_sortkey <= t1.tree_sortkey and t1.tree_sortkey between t2.tree_sortkey and tree_right(t2.tree_sortkey) and t1.object_type = :object_type) and event_type = :event_type