Ну вот напр. первые идеи:
CREATE TEMPORARY TABLE _tmp(
my_col CHAR(255)
);
INSERT INTO _tmp VALUES (\'12\');
INSERT INTO _tmp VALUES (\'2\');
INSERT INTO _tmp VALUES (\'5n\');
INSERT INTO _tmp VALUES (\'n5n\');
INSERT INTO _tmp VALUES (\'nmm\');
SELECT my_col, my_col+0 as my_col_n, IF((my_col+0), (my_col+0), (my_col+90000)) as my_col_f FROM _tmp ORDER BY my_col_f, my_col;
Мучай.....