hbaxmann: You are clearly learning relational theory in an academic setting. What school are you attending? What is your major?
For one, no one completely normalizes data in the real world, and by real world, I mean business applications. When someone does, it's clear it's a college student or grad that hasn't had the experience beyond what he learned in school. Null columns exist because the user is not always required to provide them. Like you said, it gives us the ability to detect that there is no data for it. It's a very nice concept and works really well in relational databases. There's no normalization problem because you have optional columns. If I wasn't using EJB-QL, but DynamicSQL, as someone suggested, or direct JDBC, I wouldn't have a problem at all. Using the example of customer registration, here are columns I might make optional because I wanted customers to register even if they didn't have or want to provide the information: - All address information. Definately second address line if I chose to require address information. - Second email address. - Additional phone numbers. Now, all this info could be normalized, but with an OO front-end, the benefits are near nill. Take the phone number, for instance. Phone numbers can be handled in a standard way via application objects. This mutes the benefits of normalization. However, even if I normalized it, I would still have optional foreign keys... and thus nulls. This would not resolve the problem EJB-QL has, as it applies to relationships as well as regular columns. Optional is optional, whether they are regular columns or relationships. Optionality is defined by the business requirements. If the phone number is not required information, then either a column for phone number data or a foreign key can be null. As for ER modeling, I've been developing relational applications since the early 80s prior to SQL's definition in 89. I've read quite a few books over those years, including the adademic books you're reading now, as I have a degree in IS. I've used ERwin, Oracle Designer, Rational Rose and other tools for ER modeling. Last year, I lead the effort to create a 150+ table data model for a large commercial payroll company for DB2. We used Rational Rose to create an ER model. When that was complete, we generated the data model, and then revamped it some more. Then we generated it in DB2 migrated an entire commercial payroll system to use it. It was successful. We did a lot of normalization of the data coming in, which came from the mainframe in over 100 formats. Creating a practical normalized model was one of our goals. But knowing when to normalize and when not to normalize isn't something you can learn in an academic book on relational theory. It's something you learn by repeatedly doing it in the real world for many years. Building data models for large businesses over and over again is the real world. Learning relational theory in a class is not. Using views to try to normalize a single table is rediculous in this case, both in terms of practability and the end result's ability to actually solve the EJB-QL issue. Even if it did somehow miraculously help, it would run completely counter to why I'm using CMP, and the database vendor independence required by the application. Please read comments I made earlier on why I am using CMP. It's exciting to see you learn relational theory. Clearly, you are grasping the concepts your class is teaching you. However, I highly recommend you try to learn from others who have applied it in business environments, and give them the benefit of the doubt until you have a chance to learn the practicality of some of the academic ideas when developing large business applications. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=3836518#3836518 Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&p=3836518 ------------------------------------------------------- This SF.Net email is sponsored by: Oracle 10g Get certified on the hottest thing ever to hit the market... Oracle 10g. Take an Oracle 10g class now, and we'll give you the exam FREE. http://ads.osdn.com/?ad_id149&alloc_id66&op=click _______________________________________________ JBoss-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/jboss-user
