Joomla + GROUP_CONCAT (ORDER BY, SEPARATOR)

To fetch the Joomla Categories in sorted order, GROUP_CONCAT and order by with seperator.

/* Fetching all the Childs skills into a list. */
$this->_db->setQuery($this->_db->getQuery(true)
 ->from('#__categories')
 ->select('GROUP_CONCAT(title ORDER BY lft ASC SEPARATOR ", ") as skills')
 ->where('parent_id="'.(int)$parent_id.'" AND published="1"')
 ->order('lft ASC'));
$child = $this->_db->loadObject();