postgresql7.1
select object_type as ancestor_rel_type
from acs_object_types
where supertype = 'relationship'
and object_type in (
select t1.object_type
from acs_object_types t1, acs_object_types t2
where t2.tree_sortkey like (t1.tree_sortkey || '%')
and t1.object_type = :rel_type
)