Re: Interesting article: In the Beginning: An RDBMS history
From: Jan Hidders <hidders_at_gmail.com>
Date: 7 Apr 2006 01:50:12 -0700
Message-ID: <1144399812.663448.128640_at_j33g2000cwa.googlegroups.com>
> Outside of the issue of how coupled a logical model is to the physical
> model, I see no harm in numbering the attributes provided you also name
> them.
Date: 7 Apr 2006 01:50:12 -0700
Message-ID: <1144399812.663448.128640_at_j33g2000cwa.googlegroups.com>
dawn wrote:
>
> Outside of the issue of how coupled a logical model is to the physical
> model, I see no harm in numbering the attributes provided you also name
> them.
It also makes the theory more complicated than necessary. What if we take the join of two relations, what is then the order of the attributes in the resulting table? How do you define this such that a join is still commutative? This is rather crucial for quey optimization. And what about unions? Are they allowed already if the set of attributes is the same, or does their order also have to be the same? If the orders are allowed to differ, how is then the order in the result of the union defined in such a way that we keep the usual algebraic identies?
- Jan Hidders