Re: Relational query with path expressions
Date: Fri, 3 Apr 2009 02:32:20 -0700 (PDT)
Message-ID: <6df6e795-fe71-4d68-ae23-2b4c1dad28cf_at_37g2000yqp.googlegroups.com>
On 3 avr, 05:58, David BL <davi..._at_iinet.net.au> wrote: <<I get the impression that a lot of the time, a query (or a large portion of a query) can be thought of as a navigation from attribute to attribute using a sequence of joins. This made me think there may be some merit in thinking of attribute names as global in nature and the user only has to specify the start and end attributes and the DBMS is able to deduce the joins that are required>> Sorry to be so picky but the qualification of an *operation* as a *navigation* has undertones that draw vagueness.
Your intuition however allows to rediscover the importance of definition of specialization by constraint from domains as well derived relations.
Regards... Received on Fri Apr 03 2009 - 11:32:20 CEST