postgresql 7.1 insert into secret_tokens(token_id, token, timestamp) values (sec_security_token_id_seq.nextval, :random_token, now()) select token_id, token from secret_tokens, (select trunc(random()*(select count(*)-15 from secret_tokens))::integer as first) r where token_id >= r.first and r.first+15 > token_id; update users set second_to_last_visit = last_visit, last_visit = now(), n_sessions = n_sessions + 1 where user_id = :user_id