I think what we are talking about are surrogate primary keys. http://en.wikipedia.org/wiki/Surrogate_key
Which is generally accepted as a best practice (well mostly, depending on the DBA). regards Malcolm Edgar On Tue, Feb 3, 2009 at 1:48 AM, Matt Kerr <mrmattk...@gmail.com> wrote: > > Do poeple agree w/ me here? > > yes. > > > On Mon, Feb 2, 2009 at 9:15 AM, Eric Lazarus <ericllaza...@yahoo.com> > wrote: > > I can't let this point(er) go buy: JUST SAY NO TO MEANINGFUL POINTERS! > > > > There are BIG problems with having meaningful primary keys in general in > terms of keeping your program growing and useful long term. When you can > avoid it, avoid it... and when YOU are designing the underlying database > from scratch, I think you can almost always avoid it. Putting meaning in the > pointers is often the reason that a system needs to be re-written or pitched > and replaced. > > > > A client of mine had to replace an existing application because they had > used four budget product codes as part of a pointer field and could no > longer represent the number of products in four digits. Cost huge $ to > upgrade to SAP... > > > > Here is another example, a bad choose made by apple early on, putting > data into what amounts to a pointer: > > > > http://en.wikipedia.org/wiki/Mac_OS_memory_management > > > > So, now it seems that the name and DOB of each person is not going to > change. Later it turns out that they do change under some situations and now > you have to write big hacks to deal with it. > > > > Just say no to meaning in pointers! Keep pointers STUPID! Meaningless bit > squences make great pointers in OO programs. That's my view. > > > > Of course rules are made to be broken and, when the DB exists already and > is used by a big pile of existing code, you likely have no choice but in > other situations, try to avoid meaningfulness in pointers. > > > > Do poeple agree w/ me here? > > > > Eric > > +1 (917) 589-6579 > > > > --- On Mon, 2/2/09, Pierre Lavignotte <pierre.lavigno...@gmail.com> > wrote: > > > > From: Pierre Lavignotte <pierre.lavigno...@gmail.com> > > Subject: Re: How to create Meaningful Primary Keys? > > To: user@cayenne.apache.org > > Date: Monday, February 2, 2009, 8:28 AM > > > > I don't think his question is about sequence usage but about selecting > rows > > with specific PK values... > > > > Cordialement, > > Pierre Lavignotte > > Ingénieur Conception & Développement > > http://pierre.lavignotte.googlepages.com > > > > > > On Mon, Feb 2, 2009 at 2:25 PM, Alessio Giovanni Baroni < > > alessiogiovanni.bar...@gmail.com> wrote: > > > >> It's all ok. But, you are sure that in Entity screen, you are selected > >> "Custom Sequence" on the "PK Generation Strategy"? > >> If you do it, AND you add a filed relative to a pk column, you can > > handling > >> the keys, without the cayenne's control. > >> > >> Hi. > >> > >> > >> 2009/2/2 Νίκος Παράσχου <nipar...@gmail.com> > >> > >> > 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 > > <nipar...@gmail.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 > >> > > > > >> > > > > >> > > >> > > >> > > > > > > > > >
