oracle8.1.6
insert into ec_subcategories
(category_id, subcategory_id, subcategory_name, sort_key, last_modified, last_modifying_user, modified_ip_address)
values
(:category_id, :subcategory_id, :subcategory_name, (:prev_sort_key + :next_sort_key)/2, sysdate, :user_id, :address)