[satislikev]

Hello !
In ER digram we have an assignment and our teacher forces us to use at least an IS-A relation, i Just wonder if it is possible for an entity to have is-a relationship with another entity but do not have any attribute ? For example:

An actor ISA cast.
Cast have a name.

all i need from the actor is to have a name, no date of birth, telephone number or etc.

I also attached my diagram can someone say if it have any problem or not.
P.S. we MUST use at least one ISA relation we may not use primary key,

Attached File(s)

•  TEST-Model.pdf (48.42K)
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[DarenR]

give the actor an id and use that in cast.

like cast would have the cast_name and actor_id and what ever else you want
the actor would have actor_name, actor_id, and so on.

[satislikev]

DarenR, on 26 September 2012 - 06:52 AM, said:

give the actor an id and use that in cast.

like cast would have the cast_name and actor_id and what ever else you want
the actor would have actor_name, actor_id, and so on.

I thought about that too. but if i use Actor ID , wouldn't the ID be count as a primary key?? (We may not use any primary key yet