Calusola where in un leftjoin

[piero.mac]

.....
FROM " . $this->_prefix . "tree 
LEFT JOIN " . $this->_prefix . "details 
ON " . $this->_prefix . "details.node = " . $this->_prefix . "tree.id 
WHERE quel_che_ti_pare = qualcosa
ORDER BY " . $this->_prefix . "tree.sx ASC"