Re: How will schemas be affected by nested relations?
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 24 Jul 2006 14:36:34 GMT
Message-ID: <SV4xg.14281$pu3.332630_at_ursa-nb00s0.nbnet.nb.ca>
>>How will schema design be affected by having the ability to use
>>nested relations? I have an intuition that it might not be that
>>much; that nesting is a *little* useful but not all that *much* useful.
>>However, I am concerned that I don't have a normal form to
>>inform design choices.
>>
>>When should relation schemas be nested?
>>
>>I have an idea that the answer might relate to when we use
>>ON DELETE CASCADE. If a logical entity has no existence
>>without the "enclosing" context of another entity, then it might
>>be nested. Another consideration is whether it needs to
>>be referred to directly.
>>
>>For example, an invoice line item without an associated
>>invoice doesn't make much sense. However, an invoice
>>is probably something we want to keep even if for some
>>reason we delete the associated customer. So I can see
>>invoice line items as being a candidate for nesting, but
>>not invoices.
>>
>>However I would be much happier if I had a more formal
>>treatment than this. Anyone have any references?
>>
>>
>>Marshall
Date: Mon, 24 Jul 2006 14:36:34 GMT
Message-ID: <SV4xg.14281$pu3.332630_at_ursa-nb00s0.nbnet.nb.ca>
michael_at_preece.net wrote:
> Marshall wrote: >
>>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
> > > For a more in-depth treatment of this subject please see > comp.databases.pick. > > ;) > > PS. G'day Bob.
Mike,
Marshall asked for something formal and not something braindead. Received on Mon Jul 24 2006 - 16:36:34 CEST