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$A26.374992_at_ursa-nb00s0.nbnet.nb.ca>
>
> handled
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> OTOH,
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> DOMAIN
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> I thought the diffence between a "domain" and a "type" was precisely that
> types include operators while domains do not.
Date: Thu, 01 Jun 2006 21:05:22 GMT
Message-ID: <mEIfg.16171$A26.374992_at_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
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> handled
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>>>pretty well by SQL, to the extend that SQL deals with them at all.
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> OTOH,
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>>>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
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> DOMAIN
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>>>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 - 23:05:22 CEST