public function addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete=null, $update=null)
	{
		echo "    > add foreign key $name: $table (".(is_array($columns) ? implode(',', $columns) : $columns).
			 ") references $refTable (".(is_array($refColumns) ? implode(',', $refColumns) : $refColumns).") ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete, $update);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}