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How will schemas be affected by nested relations?

From: Marshall <marshall.spight_at_gmail.com>
Date: 22 Jul 2006 01:11:08 -0700
Message-ID: <1153555868.726110.252480_at_s13g2000cwa.googlegroups.com> 





How will schema design be affected by having the ability to use
nested relations? I have an intuition that it might not be that
much; that nesting is a *little* useful but not all that *much* useful.
However, I am concerned that I don't have a normal form to
inform design choices.



When should relation schemas be nested?



I have an idea that the answer might relate to when we use
ON DELETE CASCADE. If a logical entity has no existence
without the "enclosing" context of another entity, then it might
be nested. Another consideration is whether it needs to
be referred to directly.



For example, an invoice line item without an associated
invoice doesn't make much sense. However, an invoice
is probably something we want to keep even if for some
reason we delete the associated customer. So I can see
invoice line items as being a candidate for nesting, but
not invoices.



However I would be much happier if I had a more formal
treatment than this. Anyone have any references?




Marshall
Received on Sat Jul 22 2006 - 10:11:08 CEST












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