ORM Doctrine. Выборка со случайным порядком.

// test.php

// ...
$q = Doctrine_Query::create()
    ->select('t.id, RANDOM() AS rand')
    ->from('Forum_Thread t')
    ->orderby('rand')
    ->limit(1);

echo $q->getSqlQuery();

...

SELECT 
f.id AS f__id, 
RAND() AS f__0 
FROM forum__thread f 
ORDER BY f__0 
LIMIT 1