Re: storing survey answers of different data types
Date: Fri, 24 Apr 2009 21:57:16 -0300
Message-ID: <49f25fee$0$5485$9a566e8b_at_news.aliant.net>
Joe Thurbon wrote:
> On Fri, 24 Apr 2009 14:41:12 +1000, Bob Badour
> <bbadour_at_pei.sympatico.ca> wrote:
>
>> paul c wrote:
>>
>>> Bob Badour wrote:
>>>
>>>> paul c wrote:
>>>>
>>>>> Bob Badour wrote:
>>>>>
>>>>>> Joe Thurbon wrote:
>>>>>
>>>>>
>>>>> ...
>>>>>
>>>>>>> Just wondering, if one of the requirements for a system included
>>>>>>> something like 'Be able to list all questionnaires', would
>>>>>>> you still consider one-table-per-questionairre a reasonable design?
>>>>>>
>>>>>>
>>>>>> Absolutely. It's a simple query from the system catalog.
>>>>>> ...
>>>>>
>>>>>
>>>>> How do you tell the 'questionnaire' tables from the other tables?
>>>>
>>>>
>>>> However you want.
>>>
>>> Well, it's not me, the part-time mystic, I'd like to know how a
>>> system catalog/catalogue can signify the difference.
>>
>>
>> Why does the system catalog have to signify the difference? One can
>> create any relation one wants to identify them.
>>
>>
>
> My problem with the approach is that, even if you have a way to
> identify the correct tables, it's still inconvenient to manipulate them.
>
> For example, given
>
> Catalog(TableName, IsAQuestionnaireTable)
> QTable1(...)
> QTable2(...)
> ...
>
> there is an implicit constraint that Catalog.TableName refers to tables
> that exist in the database, and another that if IsAQuestionnaireTable
> is true, that that table is a table that represents answers to a
> questionnaire. This is not encoded anywhere, and I don't think it can
> be encoded anywhere.
I cannot make sense of the above.
> I believe that that there are a class of queries that become much more
> difficult (or impossible) as well, but of course whether they are
> important would depend on requirements. For example:
>
> "What are all the answers to all of the questions to all of the
> questionnaires?"
The contents of the database.
> Maybe my question (the one I didn't manage to ask upthread) doesn't have
> a meaningful and consise answer. Maybe the question is just "How to I
> design a schema that makes the right tradeoffs for my requirements?"
> But there seems to be an issue with the approach above, because it
> makes everything 2nd order, and hence not expressible as relations.
> (How's that for an assertion without proof?)
Absurd.
> Finally, I should point out that I know we've drifted away from
> addressing the original set of requirements, and that it might well be
> the case that using 1 table per questionnaire is perfect for the OP.
> I'm really just looking for generalities.
>
> Cheers,
> Joe
Received on Sat Apr 25 2009 - 02:57:16 CEST