Re: A Logical Model for Lists as Relations
Date: Wed, 10 May 2006 11:20:48 GMT
Message-ID: <k0k8g.2132$NB6.702_at_trndny03>
"Marshall Spight" <marshall.spight_at_gmail.com> wrote in message
news:1147218113.519014.27620_at_e56g2000cwe.googlegroups.com...
> I am interested in the question of how best to handle lists in a
> relation-oriented world. I have considered various approaches,
> usually oriented around adding a list collection type.
>
This reply is way off topic, and I apologize if it's a distraction.
Oracle makes a distinction between a select that produces a result set, and
a select that produces something else, something that might well be called a
list. (I forget what Oracle documentation calls it).
The distinction is based on the presence or absence of the "ordered by
clause". A SELECT ... ORDERED BY gives a list, while the other kind gives a
set.
Other SQL DBMS products, like DEC Rdb, have no such restriction on views.
You can have a view with an ORDERED BY. You can use such a view in a
context where a set would be expected. When I do that, I get the result I
would have expected.
This seemed so intuitive to me that I scarcely realized the issue until I
moved to a product that forbids it.