Re: DBDesign Q
From: Alan <alan_at_erols.com>
Date: Mon, 24 Nov 2003 13:12:34 -0500
Message-ID: <bpthmj$1t348d$1_at_ID-114862.news.uni-berlin.de>
Date: Mon, 24 Nov 2003 13:12:34 -0500
Message-ID: <bpthmj$1t348d$1_at_ID-114862.news.uni-berlin.de>
It is correct on an ERD, but incorrect in a relational schema.
"Andy" <net__space_at_hotmail.com> wrote in message
news:edb90340.0311232036.e0eeae5_at_posting.google.com...
> Can two entities have more than one relationship between them?
>
> A(A_ID PK,..., bID FK)
>
> B(B_ID PK,..., aID FK)
>
> A.bID refers to B.B_ID
> B.aID refers to A_ID
>
> 2. Does it make sense?
>
> Product (ProductID PK, Name,., SpecialAttrID FK)
>
> Attribute (AttrID PK, Name,..,ProductID FK)
>
> Product can have many attributes. One attribute belongs to only one
product.
> There is only one main("special") attribute for each product
>
> Thank you in advance,
> Andy
Received on Mon Nov 24 2003 - 19:12:34 CET