It's seems that EOM can't model FK with more than one attributes..
So the previous question (if create two-attributes PKs) is answered...
I'll create very simple PK with one attribute of type id (sigh..)
On 30/nov/08, at 08:56, Francesco Romano wrote:
Ok.. maybe it's a bit better...
this are the two entities:
ProdottoPrivato
<Picture 1.png>
Prodotto
<Picture 2.png>
Prodotto owns and propagate the PK to ProdottoPrivato...
Now.. I've a doubt...Prodotto has its own PK and the key of the
entity MERCEOLOGIA. So.. prodotto propagates the key...?? both?
(maybe now I've a problem with the theory... if prodottoID is a
field ID (a serial) does make sense to have a foreign primary key?
In my theorical point of view I thought something like:
MERCEOLOGIA PK | Prodotto ID
1 1
1 2
2 1
but I don't think the db do something like that... Am I right? The
dbms continue to increment the prodotto_id?
Now... the last two questions...
1) It's better to have a PK with the two fields (strings) OR a PK of
type id and add a unique index on the 2 attributes? (performance,
etc..)
2) About inverse relationship... this are saved only in the class
graph, not in the db ?
I checked a one-to-many relation... even if in the migration the "n"
entity has a FK to the "1" entity, it doesn't have it in the db.
So.. How does it work? I thought migration was the "interface" to
the db...
Thanks
Francesco
On 29/nov/08, at 22:15, Miguel Angel Torres Avila wrote:
Hi Francesco
This an example of a mandatory one to one relationship, for any
prodotto it is obligated to generate a PRODOTTOESTERNO.
First you should select the owner entity, I mean the principal one.
And I suggest the use of ID's like prodotto_id instead just id.
PRODOTTO
prodotto_id PRIMARY KEY NOT NULL,
descrizione
referenza
prezzo
foto
PRODOTTOESTERNO
prodotto_id REFERENCES PRODOTTO ON DELETE CASCADE PRIMARY KEY NOT
NULL
qtaIniziale
note
In the modeler you should create a relationship from
PRODOTTOESTERNO to PRODOTTO connecting PRODOTTOESTERNO. prodotto_id
to PRODOTTO. prodotto_id.
The rules in modeler should look like this:
<Picture 2.png>
Now create a new relationship from PRODOTTO to PRODOTTOESTERNO and
the rules should look like this.
<Picture 3.png>
Now create your java Classes and Prodotto will have a
PRODOTTOESTERNO() function and PRODOTTOESTERNO will have a
PRODOTTO() function.
This way you will create a new Prodddotto's object and once you
insert it into an Editing Context the ProdottoEsterno related to it
will be created automatically.
Hope this helps.
On Nov 29, 2008, at 1:23 PM, Francesco Romano wrote:
Hi...
I'm having some problems passing from the "teorical" ER model , to
design the real model using EOModeller.
Using the Entity-Relationship model I designed the following tables:
MERCEOLOGIA (nome,marca)
PRODOTTO (id,descrizione, referenza, prezzo, foto )
LUOGO (nome)
PRODOTTOESTERNO (PRODOTTO, qtaIniziale, note)
DISPONIBILITA (PRODOTTO,descrizione)
LUOGO-PRODOTTO (luogo, prodotto, quantita)
Where: the uppercase word is the Entity, between the brackets
there are the attributes. The underlined words are the Primary Keys.
So..
MERCEOLOGIA has a 1-to-many relation with PRODOTTO, with the PK of
PRODOTTO is id and the PK of MERCEOLOGIA
LUOGO and PRODOTTO has many-to-many relation (plus an attribute)
PRODOTTOESTERNO has a one - to-one relation with PRODOTTO. The PK
of PRODOTTOESTERNO is the PK of PRODOTTO
DISPONIBILITA has a one-to-many relation with PRODOTTO.
I've no problem if EOM create a "id" PK for every entity.. I add a
Unique key on my "teorical" PK and solve this problem...
but...
I don't know how to create one-to-one relations (I can't add them
using the button..) and how to model the "foreign" PK..
Can somebody please help me solving this?
Thanks
Francesco
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