Re: How to create Meaningful Primary Keys?

From: Νίκος Παράσχου (niparas..mail.com)
Date: Mon Feb 02 2009 - 08:14:45 EST

  • Next message: Pierre Lavignotte: "Re: How to create Meaningful Primary Keys?"

    First of all thank you for your replies.

    I have the following table:

    Vehicle (
           plate_num CHAR(10) NOT NULL,
           mixed_weight DOUBLE PRECISION NOT NULL,
           type CHAR(30) NOT NULL,
           manufacturer CHAR(20),
           PRIMARY KEY (plate_num)
    )

    In Cayenne Modeller I have the dbEntity "vehicle" with all the above
    attributes (plate_num is check as PK). There is also the objEntity
    "Vehicle" with all the above attributes except the PK (plate_num).

    I want to select the type of the vehicle with plate_num = "AHZ-4141".

    Could you please post some code samples? I have tried so many things
    (with DataObjectUtils too) but still no success.

    Thank you,
    Nikos

    Στις 02-02-2009, ημέρα Δευ, και ώρα 12:49 +0100, ο/η Pierre Lavignotte
    έγραψε:
    > Hi Nikos,
    >
    > If you need PK for all your tables, then maybe you need to generate them.
    > But if you only need to use them for a couple tables then you should look at
    > DataObjectUtils class.
    >
    >
    > Cheers,
    > Pierre
    >
    > Cordialement,
    > Pierre Lavignotte
    > Ingénieur Conception & Développement
    > http://pierre.lavignotte.googlepages.com
    >
    >
    > On Mon, Feb 2, 2009 at 12:35 PM, Νίκος Παράσχου <niparas..mail.com> wrote:
    >
    > > Hello,
    > >
    > > It is the first time I am using cayenne and I have some questions
    > > regarding the primary keys.
    > >
    > > What I want to do is select some rows of a table where the PK has a
    > > specific value. The problem is I can't access the PK. I can specify
    > > qualifiers only with the non-PK columns. The PKs I am using have some
    > > meaning (they are not just numbers) so it is very important to be able
    > > to use them.
    > >
    > > How can I add the PK to the fields of the Object Entities?
    > >
    > > In this page http://cayenne.apache.org/doc20/primary-key-generation.html
    > > the answer is to create a Meaningful Primary Key.
    > >
    > > How can I create Meaningful Primary Keys?
    > >
    > > Are there any security issues when using Meaningful Primary Keys?
    > >
    > > Thank you for your time,
    > > Nikos
    > >
    > >

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