Re: Database development

From:

Robert Klemme <shortcutter@googlemail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 28 Apr 2010 00:30:26 -0700 (PDT)

Message-ID:

<2889713e-9bf0-4372-9c67-afbafac16c46@z7g2000yqb.googlegroups.com>

On 28 Apr., 03:43, Arne Vajh=F8j <a...@vajhoej.dk> wrote:

On 27-04-2010 12:06, Robert Klemme wrote:

On 27 Apr., 02:31, Arne Vajh=F8j<a...@vajhoej.dk> wrote:

On 26-04-2010 16:14, Robert Klemme wrote:

Btw, did I mention that I believe database independence is a myth? :-=

)

It is a myth that is seen working everyday in the Java world, that
many Java apps using a good ORM (like Hibernate or one
of the JPA implementation) use the same Java code with different
databases. It is not always that easy. But for all the simple
stuff it works well.

Hm... The question is: how simple is "simple" and where does
"complicated" begin? Just an example, which I would rather place in
the "simple" bucket: assume you want to query for items that have a
field set to null. Considering that Oracle does not index NULL value=

and another RDBMS that you want to use does so, you'll likely end up
with a clutch: either you use a different value for NULL which will
allow for uniform ORM code at the cost of a bad design; or you need to
make the ORM tool create different queries (and I do not mean the
difference between "VARCHAR2" and "VARCHAR") for Oracle and the other
RDBMS. You could, of course, also live with the FTS in Oracle but I
doubt you'll have much fun doing this on any reasonably large
database. :-)

How does you solve it by using JDBC?

Well, you would either wrap the query in a stored procedure or use
custom SQL per database engine type. For example, with Oracle you
could create a FBI and query with its functional expression.

In any case I believe the complicated stuff is where the fun begins -
so for _me_ DB independence is definitively a myth. ;-)

Well - out goal is to make everything as simple as possible.

.... but not simpler. :-)

Cheers

robert