I have this ER diagram, which supposedly has two cycle relationships. I have doubts because one person says that...
it is indeed cycle relationships, and another person says that it does not. The diagram can be found at: http://www.jmontalvo.com/registrations1000x900.jpg.
You diagram is really hard to read on a 160 by 160 display, but the only circular reference I can see (where an entity contains its own Primary Key as a Foreign Key too) is AppUser. You could create a true circular reference there.
A cycle relationship is more complex, where some group of entities refer to each other in such a way that it is possible to create a "loop" of relationships that feed back into itself. There are several possible 1:N relationships that could generate a cycle, but I can't see how they would naturally assume a cycle.
The short answer is yes, a cycle is possible in more than one way, but I don't see how it would occur naturally.
For More Information
- Dozens more answers to tough database design questions from Pat Phelan
- The Best Database Design Web Links: tips, tutorials, scripts, and more
- Have an administration or SQL tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize. Submit your tip today!
- Ask your database design questions -- or help out your peers by answering them -- in our live discussion forums.
- Ask the Experts yourself: Our SQL, database design, SQL Server, DB2, object-oriented and data warehousing gurus are waiting to answer your toughest questions.
Dig Deeper on Oracle database design and architecture
Related Q&A from Pat Phelan
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.