Re: Interpretation of Relations
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 15 Feb 2007 13:12:03 GMT
Message-ID: <D_YAh.6726$R71.101481_at_ursa-nb00s0.nbnet.nb.ca>
>
> Thanks go to all who contributed to this thread. I've got some books
> ordered from at local bookstore, and thanks in particular to paul c, who
> passed on some really useful references.
>
> By the way, I also found my old Uni textbook (ha, I told my wife it
> would come in useful one day). It's Fundamentals of Database Systems by
> Elmasri and Navathe. Could anyone who is familiar with it give me some
> sort of idea about its usefulness. I'm particularly concerned with page
> 137:
>
> "where each value is an element of dom(Ai) or is a special null value".
Date: Thu, 15 Feb 2007 13:12:03 GMT
Message-ID: <D_YAh.6726$R71.101481_at_ursa-nb00s0.nbnet.nb.ca>
Joe Thurbon wrote:
>> I'm very new to this databases game, and am not even sure I'm using >> the terminology in the right way. I'd like some feedback as to whether >> I'm even in the right ballpark. Most of my understanding of the >> terminology comes from reading this group, and the definitions on >> Wikipedia.
>
> Thanks go to all who contributed to this thread. I've got some books
> ordered from at local bookstore, and thanks in particular to paul c, who
> passed on some really useful references.
>
> By the way, I also found my old Uni textbook (ha, I told my wife it
> would come in useful one day). It's Fundamentals of Database Systems by
> Elmasri and Navathe. Could anyone who is familiar with it give me some
> sort of idea about its usefulness. I'm particularly concerned with page
> 137:
>
> "where each value is an element of dom(Ai) or is a special null value".
One general caveat: Academic books often give rigorous definitions for terms that might differ from one text to another. For example, I often see contradictory definitions for 'candidate key'. Strangely, some texts use the term for teaching about proper superkeys and irreducibility while others use the term for teaching about the possibility of multiple logical identifiers.
To a certain extent, one has to preface all of those definitions with "Within the scope of this book/course". Received on Thu Feb 15 2007 - 14:12:03 CET