Re: delete cascade

Bob Badour wrote:
> paul c wrote:

>>
>> ... 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.

I think they are mixing (DBMS) capabilities and language issues.

> I look at that and ask: Is the join theoretically updatable?

Which is an uninteresting question, because both paulc's interpretation and Bob's, this one:

> I look at that and ask: Is the join theoretically updatable? And I
> answer with: "Yes, not only is it updatable but we have our choice of
> update strategies."

seem quite acceptable.

> Granted, absent any other information, one has no theoretical reason to
> favor one update strategy over another, which is why a dbms must provide
> some means to express

s/express/accept/

> whatever additional information is necessary to
> disambiguate the situation.

Most DBMS already have this (accept) capability. The language the user or the program uses to interact with the DBMS to access their data should provide the freedom to express the usage of these capabilities.

This may seem like a nitpick. To me the issues are clearly distinct, and but I often encounter this (what I consider a) blur. Received on Mon Apr 23 2007 - 01:14:54 CEST