Re: XQuery question

From: Kenneth Downs <MyUseNetHandle_at_linuxmail.org>
Date: Mon, 19 May 2003 20:49:53 -0400
Message-ID: <6hubab.85u.ln@mercury.downsfam.net>

Quoting unnamed sources, Neo claimed:

>> Given meta-data tables that describe relations between tables, and the
>> names of two columns in any two tables, determine if a set of JOIN
>> conditions can be constructed for a generated SELECT statement.

>
> I see the potential use, but wouldn't that be a very limited graph
> since according to Date's 6th Ed "Intro to Db Sys" each tuple's
> attribute is based on a domain and domains are defined as having
> scalar values, or has this been corrected? If domains have scalar
> values, wouldn't the number of levels to determine whether two
> attributes are joinable always be the same?

You are probably right. An example was asked for, an example was given.

>

>> ... "describe relations between tables" ...

>
> Since the relational data model (rdm) defines a "relation" as being a
> set of tuples which is generally conceptualized as a table, the above
> sentence in rdm-speak would translate to "tables between tables" which
> is probably not what you meant. What word did rdm formally assign to
> the word "relation" as used in the above sentence? Surely rdm has a
> formal word for that very basic and fundamental concept.

See Tom's reply.

-- 
Kenneth Downs

Received on Mon May 19 2003 - 19:49:53 CDT