CakePHP2.x系ではORMが便利で直接SQLを記載する事はあまりありませんが、複雑になるなど、どうしても直接SQLを記載する時があると思います。
以下でいけます。fetchAllです。
<?php
public function querySelectCommentsReplies($torettaId) {
$db = $this->getDataSource();
$sql = "SELECT
TorettasComment.id,
TorettasComment.user_id,
TorettasComment.comment,
TorettasComment.created,
TorettasCommentsReply.id,
TorettasCommentsReply.user_id,
TorettasCommentsReply.torettas_comment_id,
TorettasCommentsReply.reply,
TorettasCommentsReply.created
FROM
torettas_comments AS TorettasComment
LEFT JOIN
torettas_comments_replies AS TorettasCommentsReply
ON TorettasComment.id = TorettasCommentsReply.torettas_comment_id
WHERE
TorettasComment.toretta_id = ?
";
$result = $db->fetchAll($sql, array($torettaId));
return $result;
}

