public function update ($record){
   $query = 'UPDATE _entity_has_element SET 

 where  entity_id'.($record->entity_id===null ? ' IS NULL ' : ' = '.intval($record->entity_id)).' AND element_id'.($record->element_id===null ? ' IS NULL ' : ' = '.intval($record->element_id)).' AND role_id'.($record->role_id===null ? ' IS NULL ' : ' = '.intval($record->role_id)).'
';
   return $this->_conn->exec ($query);
 }