[noppid]

That query will/could bring a forum to it's knees running every page view.

mysql> explain Select * From thread order by rand() DESC LIMIT 1
    -> ;
+----+-------------+--------+------+---------------+------+---------+------+------+---------------------------------+
| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows | Extra                           |
+----+-------------+--------+------+---------------+------+---------+------+------+---------------------------------+
|  1 | SIMPLE      | thread | ALL  | NULL          | NULL | NULL    | NULL | 6026 | Using temporary; Using filesort |
+----+-------------+--------+------+---------------+------+---------+------+------+---------------------------------+
1 row in set (0.03 sec)

As you can see, a full table walk.

Here's a better way.

60*60 == 3600
3600*24 == 14400
14400*30 == 432000
1223479602 - 432000 == 1223047602

mysql> explain Select * From thread where dateline >= 1223047602 order by dateline DESC limit 1;
+----+-------------+--------+-------+---------------+----------+---------+------+------+-------------+
| id | select_type | table  | type  | possible_keys | key      | key_len | ref  | rows | Extra       |
+----+-------------+--------+-------+---------------+----------+---------+------+------+-------------+
|  1 | SIMPLE      | thread | range | dateline      | dateline | 4       | NULL |  104 | Using where |
+----+-------------+--------+-------+---------------+----------+---------+------+------+-------------+
1 row in set (0.00 sec)

See the difference? Gotta use those indexes. Rand() is bad.