Nested Sets

protected function prepareTable($table)
{
       jimport('joomla.filter.output');
       $db = JFactory::getDbo();

       // Specify where to insert the new node.
       $parent = @$table->parent_id;
       if (!empty($parent))
       {
           $table->setLocation($parent, 'last-child');
       }
       else
       {
           $rootId = $table->getRootId();
           if ($rootId === false)
           {

               $db = JFactory::getDbo();
               $sql = 'INSERT INTO #__yomo_ussd_article_category'
                   . ' SET parent_id = 0'
                   . ', lft = 0'
                   . ', rgt = 1'
                   . ', level = 0'
                   . ', title = '.$db->quote('root')
                   . ', alias = '.$db->quote('root')
                   . ', access = 1'
                   . ', path = '.$db->quote('')
               ;
               $db->setQuery($sql);
               $db->query();

               $parent = $db->insertid();
               $table->setLocation($parent, 'last-child');
           }
           else
           {
               $table->setLocation($rootId, 'last-child');
           }

       }

       # Check that the node data is valid.
       $table->check();

       # Store the node in the database table.
       $table->store();
}