Re: Question: Entities With Common Attributes

David Hay has good examples in his book but he has a supertype table called customer and two subtype tables that are individual and corporate. It seems that there are several attributes of a general customer like address, phone etc. and some that are common to individuals and some to customers. It becomes an IS-A relationship and is modeled with a primary key and foreign key.

David Olsen

SQL-er wrote:

> Thanks in advance for any suggestions offered:
>
> All right, I *thought* I understood database modelling and SQL, until the
> following arose:
>
> What is the "accepted way" of handling something like this ?
>
> A database model for a company sales obviously contains an entity "customer"
>
> But, in this case, there are 2 types of customer - "businesses" and
> "individuals"
> Different attributes are recorded for each type
>
> eg: something like:
>
> Individual-Customer
> Customer-number
> Name
> Phone-no
> Driving-Licence-number
>
> Business-Customer
> Customer-number
> Business-name
> Business-type
> phone-no
> fax-no
>
> So, the customer-number is the only attribute common to both types of
> customer
> But, I don't see how that ought to be handled
>
> I'm probably missing something very obvious here...
> Could someone give me a hint as to what it is ?
>
> novice SQL-er ( still learning )
Received on Thu Apr 05 2001 - 02:36:51 CEST