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Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

From: Lauri Pietarinen <lauri.pietarinen_at_atbusiness.com>
Date: Mon, 10 Mar 2003 20:54:58 +0200
Message-ID: <3E6CDF82.7040607@atbusiness.com>


Jan Hidders wrote:

>Lauri Pietarinen wrote:
>
>
>>Jan Hidders wrote:
>>
>>
>>>Lauri Pietarinen wrote:
>>>
>>>
>>>
>>>>I can't get into all the details here but there
>>>>there is lot's of discussion on different issues relating
>>>>aggregates in
>>>>Relational Database Writings 1994-1997
>>>>(ISBN 0-201-39814-1) installments 44, 45 and 50.
>>>>
>>>>
>>>I'm not much impressed by those references. The whole point of our
>>>discussion was to see how well their arguments stand up to critical
>>>examination. Since you apparently don't want to go into the specific issue
>>>that we were disussing I now get the feeling that you want to avoid that
>>>discussion.
>>>
>>>Pity.
>>>
>>>
>>I was not really trying to impress you by those references. I was just
>>figuring that since we were talking about aggregates we should have some
>>reference (if not agreement) as to what an aggregate function means.
>>
>>
>
>Why do you think there is disagreement about that?
>

Well, from reading those articles by Date I don't get the impression that bags provide more
optimisations than sets regarding aggregates as you suggested.

>>Regarding sets<-->bags in general I would sum up my arguments followingly:
>>
>>1) SQL operates in two modes: "bag"-mode and "set"-mode
>>
>>
>
>Where do you get this idea from? There is just one mode: the bag mode.
>

 From the users point of view there are two modes. Call them "user visible modes" that are hidden
from the system, if you like.

>>Regarding point 5) I challenge you to give me just
>>*one* *real* *world* *example* in which duplicates
>>would actually be of use to the end user.
>>
>>
>
>I never said there was, and even if there was you could simulate this in a
>set-only model.
>
>So, what is your point exactly?
>

If nobody needs them (bags) why support them? Even if the cost is zero?

regards,
Lauri Pietarinen Received on Mon Mar 10 2003 - 12:54:58 CST

Original text of this message

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