Как определить натуральные числа

CREATE TABLE Nothing ( God XML );

— ноль
SELECT count(*) AS X FROM
    Nothing;

— один
SELECT count(*) AS X FROM
    (SELECT count(*) AS X FROM Nothing) X;

— два
SELECT count(*) AS X FROM
    (SELECT count(*) AS X FROM Nothing
     UNION
     SELECT count(*) AS X FROM (SELECT count(*) AS X FROM Nothing) X) X;

— и так далее ...