$query
  ->select($db->quoteName(array('a.id', 'a.introtext', 'a.alias', 'a.catid', 'a.published', 'a.created')))
  ->select($db->quoteName('b.id', 'idCat'))
  ->select($db->quoteName('b.alias', 'catAlias'))
  ->select($db->quoteName('b.name', 'catName'))
  ->from($db->quoteName('#__k2_items', 'a'))
  ->join('LEFT', $db->quoteName('#__k2_categories', 'b') . ' ON (' . $db->quoteName('a.catid') . ' = ' . $db->quoteName('b.id') . ')')
  ->where($db->quoteName('a.catid') . ' IN ('. $id . ')  AND ' . $db->quoteName('a.published') . ' = '. 1)
  ->order($db->quoteName('a.created'), DESC)
  ->setLimit(10);
echo $query;

SELECT `a`.`id`,`a`.`introtext`,`a`.`alias`,`a`.`catid`,`a`.`published`,`a`.`created`,`b`.`id` AS `idCat`,`b`.`alias` AS `catAlias`,`b`.`name` AS `catName` FROM `jk2_k2_items` AS `a` LEFT JOIN `jk2_k2_categories` AS `b` ON (`a`.`catid` = `b`.`id`) WHERE `a`.`catid` IN (14) AND `a`.`published` = 1 ORDER BY `a`.`created` DESC LIMIT 10