Re: Help with this db design
Re: Help with this db design
- Subject: Re: Help with this db design
- From: Gustavo Pizano <email@hidden>
- Date: Sat, 22 Mar 2008 09:45:30 -0500
Aha ok, Im correcting all the naming errors.
I still don't get it about the PersonXConvetion - Person and
Convention tables.
On Mar 21, 2008, at 11:26 PM, Guido Neitzer wrote:
On 21.03.2008, at 19:39, Gustavo Pizano wrote:
in PersonXconvoc I have those attributes as pk, so a Person can be
in different convocations just once.
If you have more than just a plain join table with two keys, I would
always have a separate pk for that table and the two others would
just be foreign keys. You still model a m:n relationship with that,
it can have properties.
if I do that, i understand you mean something like this, no?
if that's so. then I can have the following data.
id id_person id_convocation
1 01 1
2 01 1
which its not accepted because a person can't be twice in the same
convocation.
Im checking the relationship of this 2 tables and don't see the m:n ,
im gonna make the relationships again and take care about that
relationship.
As JVF said "You will have to model the middle table as an entity by
itself, so give it a meaningful name (?Assignment?Meeting?
Appointment?). You will end up with Person <-->> ?Appointment? <<-->
Convocation."
I know that, but I though that middle table was PersonXConvocation.
Im not getting it there... :(
Gus
PS I changed the study_level_id to id_study_level already, just that
its not reflected on the picture.
It is not strictly necessary to do this, but your life will be
miserable in EOF if you don't create a seperate pk there.
And to be consistent you should make the attribute "id_study_level",
then you are consistent with your other foreign keys.
cug
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