You have GOT to be kidding me--bringing down a database should be the last
possible thing you consider, particularly if this database has any kind of a
user population greater than 1.
The problem with the "reserved columns" approach is multifold:
1) Column names aren't indicative of data stored.
2) No relational integrity can be applied to the columnar data, since we
don't know what the relationships are yet.
3) Columnar data must be stored in some "transparent" fashion, usually
either a string or a blob, which leads to having to translate the data to
and from the database (if it's an int value, for example).
Most of the major databases will allow you to *add* to the schema without
having to drop the database, but in general, whenever you're looking at a
schema change, you're looking at a major happening. Some Object-Relational
mapping layers have taken to storing the objects directly into the database
as binary columns, but this is another last-resort idea, since it means that
you lose the ability to do SQL queries on object attributes (which is part
of the whole reason you store data in an RDBMS in the first place, right?
:) ).
In short, this is *not* an easy problem to solve. Your DBA should be praised
for raising it. Now the question to your EJB vendor becomes how do *they*
want to deal with it? Some, if they created the schema in the first place,
will do some pretty drastic things that will anger and annoy your DBA if
you're not careful.
Ted Neward
{.NET || Java} Course Author & Instructor, DevelopMentor
(http://www.develop.com)
http://www.javageeks.com/tneward
http://www.clrgeeks.com/tneward
----- Original Message -----
From: "Ara Abrahamian" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, April 16, 2002 10:10 AM
Subject: Re: [EJB-INT] 3rd normal form & EJB
> If you really care about it you can add some dummy/reserved columns of
> common types. Don't use them now, but when you need a new attribute just
> use one of those reserved columns!! I've seen this trick in an RPG app
> ;-) But who cares about this issue? Just bring down the server for
> maintenance and update the database.
>
> Ara.
>
> > -----Original Message-----
> > From: A mailing list for Enterprise JavaBeans development [mailto:EJB-
> > [EMAIL PROTECTED]] On Behalf Of Mindaugas Kairys
> > Sent: Tuesday, April 16, 2002 1:29 PM
> > To: [EMAIL PROTECTED]
> > Subject: 3rd normal form & EJB
> >
> > Hello,
> > I have such philosophical, but real problem. My Oracle admin asks me,
> why
> > are you using such plane database design, what will you do, when it
> will
> > come the need for new object attributes: alter tables, change program
> > code,
> > stop server....?
> >
> > I'd wanted to hear opinions, suggestions, the ways you solve that
> problem
> > from you and ask what tools, tips, patterns one should use to archieve
> > database design of 3rd normal form normalization level using EJB? I
> know
> > that CMP entity EJB will be solution to achieve that, but it takes too
> > much
> > time. Mhm...
> >
> > Mindaugas Kairys
> >
> >
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>
>
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