If the prices for a service change depending on the date, this can be recorded in a view that contains a field for the service ID, a field for the date and a field for the price. The field for the service ID is the non-time-dependent part of the key and the field for the date is the time-dependent part of the key. If the view has maintenance status ‘M’, you can insert records whose service ID is identical to that of existing records. However, you cannot insert records with new IDs.