Re: delete cascade

Bob Badour wrote:
> ...
> Consider base relations you would likely find familiar with an Invoice
> relation, an InvoiceItem relation, and a foreign key reference from
> InvoiceItem to Invoice.
>
> In the first case, consider application views that essentially mirror
> the base relations. If someone tries to delete an invoice while invoice
> items remain, the dbms will balk with an error due to the foreign key
> constraint.
>
> In a second case, consider an application view that groups the invoice
> items as an RVA of each invoice. If one deletes an invoice, one deletes
> the invoice items at the same time and the dbms will not balk.
> ...

(Haven't thought of a reply to the rest of the post yet but regarding the above, I must bring up a sidetrack even though I don't understand it - I believe some people say that you shouldn't delete from such a view, assuming it is defined by using join. I gather their reason is that there isn't just one set of changes to the base tables that will falsify the tuples in the view, eg., it would be enough to delete just the base invoice items and not the base invoices to make the view empty and they would like a logical reason for that decision compared to deleting from both base tables or vice-versa.)

p Received on Sun Apr 22 2007 - 18:15:24 CEST