Re: Cyclical Relation.

kk wrote:
>
> Hi Friends, i've a little problem with a database design, and i've found
> several solutions....but i'd like to heard from you...
>
> The example is really easy...
>
> User Message
> -------- --------
> IdUser IdMessage
> Name Date
> Title
> Body
>
> Each User has some data that is only for that user like readed, active....
>
> What E/R Model should cover this and without finishing in a cyclical
> relation between User and Message.. If....
>
> Send Action
> 1 user can send 1 or many messages
> 1 message can be sent by only 1 user
>
> Receive Action
> 1 user can receive 1 or many messages
> 1 message is owned by 1 user.

Sounds like you need two user fks in Message: IdUserSent
IdUserRecipient

These are no cyclic relations, because they go from User to Message twice. To be cyclic (as I understand it) they would have to go from User to Message and back.

hth,
Heinz Received on Tue Apr 24 2001 - 14:12:32 CEST