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Home -> Community -> Usenet -> comp.databases.theory -> Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 01 Jun 2006 21:05:22 GMT
Message-ID: <mEIfg.16171$A26.374992@ursa-nb00s0.nbnet.nb.ca>


David Cressey wrote:

> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
> news:uwHfg.16134$A26.374329_at_ursa-nb00s0.nbnet.nb.ca...
>

>>David Cressey wrote:
>>
>>
>>>"Cimode" <cimode_at_hotmail.com> wrote in message
>>>news:1149188800.056087.159770_at_h76g2000cwa.googlegroups.com...
>>>
>>>
>>>>Thank you for your feedback...
>>>>
>>>><<This is urban myth. SQL is widely criticised for its NULL and
>>>>duplicate
>>>>treatment. There is several more little annoying inconsistencies. >>
>>>>"myth" seems a strong word to me...It's true that SQL very apparent
>>>>drawbacks consists of poor duplicates treatment and poor handling of
>>>>missing data (NULL) but I do not believe these are the worst.  Other
>>>>drawbacks appear more troubling to me into handling better relational
>>>>requirements are the fact that SQL neither correctly support domain
>>>>definition, nor it implements any real coherence of what relational
>>>>data types are.
>>>>The main impact is that a better integrity preservation, a core issue,
>>>>becomes very difficult to implement.
>>>
>>>I'm not following the above.  Bad duplicate treatment can be avoided by
>>>judicious use of primary keys and the "distinct" feature.  NULLS are

>
> handled
>
>>>pretty well by SQL,  to the extend that SQL deals with them at all.

>
> OTOH,
>
>>>some of the SQL DBMS products don't deal with missing data very well.
>>>
>>>But what really baffles me is "lack of domain definition"?  CREATE

>
> DOMAIN
>
>>>seems pretty straightforward to me...
>>>am I missing something?
>>
>>I think you are missing the part where a domain is an arbitrary data
>>type complete with its own set of operations. You seem to have confused
>>the relational domain with the rudimentary aliasing facility that
>>actually made it into SQL using a similar name.

>
> I thought the diffence between a "domain" and a "type" was precisely that
> types include operators while domains do not.

I am not sure where you got that idea. It is not my understanding at all. Received on Thu Jun 01 2006 - 16:05:22 CDT

Original text of this message

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