- values += ",modified_at={:f}".format(modified_time)
- cmd= "UPDATE " + table + " SET " + values + " WHERE " + self.__create_where(WHERE)
+ values += "{}modified_at={:f}".format("," if values else "", modified_time)
+ cmd = "UPDATE " + table + " SET " + values + " WHERE " + self.__create_where(WHERE)