oracle8.1.6
update ml_mailing_list_user_map
set subscribed_p = 'f',
unsubscription_date = sysdate
where list_id = :list_id
and user_id = :user_id
insert into ml_mailing_list_user_map
(list_id, user_id, subscribed_p, subscription_date)
values (:list_id, :user_id, 't', sysdate)
update ml_mailing_list_user_map
set subscribed_p = 't',
subscription_date = sysdate
where list_id = :list_id
and user_id = :user_id