Apple

On Jun 18, 2008, at 7:33 PM, Ren, Kevin wrote:

Hi,

My question is coming from "SQL generation" in Entity Modeler.
When I am playing the code with Apple/example/SophisticatedDatabaseExample.

Both EOModeler and Entity Modeler take the approach that they are speaking JDBC, not any database-specific SQL. There are, of course, plugins that can make the behavior of any of the EOAdaptors more sophisticated. I do not think that Entity Modeler promises to do everything it could do to create the optimal SQL for any particular database and schema.

A couple of things. If you know what you want, you can probably add the proper constraints yourself. EOF's primary job is to give you an object graph, not to do database design.

Also, if you want to suggest changes to any of the plugins in PWO, you could. The new SQL implemented there would have to not break anyone else.

I would also ask if all the complexity allowed in your database needs to have a place in the model. A model provides an abstraction. Perhaps the model could be kept simpler for greater flexibility in the future.

But then again, EOF and Entity Modeler could always do better. Sometimes the tools just really do the most minimal job and more could be done.

cheers - ray

Copied from README:
The SophisticatedDatabaseExample demonstrates the use of inheritance, flattening, and multiple models.

The Person class is abstract. Student, Parent and Employee inherit from Person using horizontal inheritance.
The Admin,Staff, Teacher classes all inherit from Employee using single-table inheritance.
The HomeAddress, WorkAddress, and BillingAddress inherit from Address using vertical inheritance.

The relationship between Student and ScheduledCourse is an example of a many-to-many "flattened" relationship. The normal indirect "join" table values are extracted into each side of the relationship, giving the appearance of a direct many-to-many relationship between entities(classes). This relationship is interesting because Student is an entity in the School model but ScheduledClass is an entity in the Course model.

When I tried to create foreign key constraints using "Generate SQL", I only got some constraints, not all of them.
All I got from two models:
ALTER TABLE SCHEDULED_CLASS ADD CONSTRAINT SCHEDULED_CLASS_SCHEDULE_FK FOREIGN KEY (SCHEDULE_ID) REFERENCES SCHEDULE (SCHEDULE_ID);

ALTER TABLE SCHEDULED_CLASS ADD CONSTRAINT SCHEDULED_CLASS_COURSE_FK FOREIGN KEY (COURSE_ID) REFERENCES COURSE (COURSE_ID);

ALTER TABLE SCHEDULED_CLASS ADD CONSTRAINT SCHEDULED_CLASS_CLASSROOM_FK FOREIGN KEY (CLASSROOM_ID) REFERENCES CLASSROOM (CLASSROOM_ID);

ALTER TABLE STUDENTPARENT ADD CONSTRAINT STUDENTPARENT_STUDENT_FK FOREIGN KEY (PARENT_ID) REFERENCES STUDENT (PERSON_ID);

ALTER TABLE STUDENTPARENT ADD CONSTRAINT STUDENTPARENT_PARENT_FK FOREIGN KEY (PARENT_ID) REFERENCES PARENT (PERSON_ID);

ALTER TABLE STUDENT_SCHEDULED_CLASS ADD CONSTRAINT STUDENT_SCHEDULED_CLASS_STUDENT_FK FOREIGN KEY (STUDENT_ID) REFERENCES STUDENT (PERSON_ID);

I think some foreign key constraints are missing, like
SCHEDULED_CLASS and TEACHER(EMPLOYEE), EMPLOYEE and ADDRESS, STUDENT and STUDENT_SCHEDULED_CLASS …..

Is it bug in Entity Modeler or somewhere couldn't figure out the horizontal/vertical inheritance in the model?

Thanks

Kevin

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