Re: Why all the max length constraints?
Date: Sun, 28 May 2006 13:57:10 GMT
Message-ID: <W_heg.41233$mh.4214_at_tornado.ohiordc.rr.com>
dawn wrote:
> J M Davitt wrote:
>
>>dawn wrote: >> >>>J M Davitt wrote: >>> >>>>dawn wrote: >>>> >>>>>[OK, here is my next "stupid question" as I cut a path in my study of >>>>>the RM. Those teachers who just want to tell this student how ignorant >>>>>she is are welcome to sit this out as I really am hoping to >>>>>understand.] >>>> >>>>[Quiz time: what are scalars, tuples, and relations?] >> >>It's a quiz. These are fundamental terms in the relational model.
>
> Yes, I know. Why do you think I could not define them? I've provided
> definitions, likely for each of these, for the glossary at one time or
> another, along with defs for "functions" which are relations.
>
> I have read quite a bit about the RM (including TTM and almost all of
> Date's 8e). My questions are typically about topics not covered in
> such places and are all about the application and usefulness of the
> theory related to databases. They stem from having had a belief that
> the RM was the way to go and then seeing how much more bang for the
> buck at least one non-RM-database model was for a company. So, I'm
> trying to square up what I've learned in the real world with the theory
> that has driven the database industry for the past couple of decades.
> There is still a gap, but I'm understanding a bit more where the
> implementations of the RM have taken the industry a bit astray from
> what I have seen as best practices (2VL, LVAs, variable length
> variables, for example).
I had added the pop quit to my response after finishing what appeared later. The reason? Well, if you knew what scalars, tuples, and relations were, you would be able to answer your own question: there is nothing in the definitions of these that, in any way, limits the size of stored data.
As for "implementations of the RM [that] have taken the industry a bit astray:" should we understand that you think that some implementation of the relational model used something other than two-valued logic? That list-valued attributes - if I understand the abbreviation - represent a "best practice?" That variable length variables - let alone variable variables - have somewhere been left behind?
Please, tell us exactly, which implementations of the relational model have done this?
[snip] Received on Sun May 28 2006 - 15:57:10 CEST