postgresql7.1
select c.category_id as link_category_id
from categories c
where c.category_id in ([join $link_category_id ,])
and acs_permission__permission_p(c.tree_id,:user_id,'category_tree_write') = 't'
and c.category_id <> :category_id
and not exists (select 1
from category_links l
where l.from_category_id = :category_id
and l.to_category_id = c.category_id)