Can we create a primary key in an instance where there are multiple primary keys (Appointments table). So we can link it to the relevant tables. Thanks

Hi Reuben, Absolutely, you can have a composite primary key in the Appointments table if you deem it necessary. For instance, if there's a relationship between appointments, patients, and surgeons, you can designate an attribute (think of which attribute) as the primary key or partial primary key within the appointment entity. This remains true even if additional attributes are needed later on in the physical design phase to create a composite primary key. "Reuben Stanley" <23*7*3*5@s*u*e*t*u*a*e*u*a*> wrote:

Great, thanks. Also are we allowed to create a relationship between subclasses? I have set up the Client superclass with patient and customer subclasses, so am I able to create a customerID (seperate from the ClientID), that I can link to the patient table so that the patient can have a record who is paying for their appointment? And just to clarify, I know we aren't meant to note foreign keys, but do we include them as regular attributes in the entities? For example can I include the patients identifier in appointments entity? Thank you

Yes, you can have a relationship between subclasses. As far as including foreign keys as regular attributes, do not do that. Whenever, you are doubt, check the ERD in the dreamhome case study. Cheers Mehwish