Re: sql views for denormalizing
Date: Sat, 30 Jul 2005 07:34:01 GMT
Message-ID: <J3GGe.21$585.11_at_read3.inet.fi>
dawn wrote:
> oops, thought I'd correct typo in subject line.
> dawn wrote:
>
>>This is another question on the topic about which I have been most
>>perplexed -- 1NF.
>>
>>Because we want to report against or view data potentially in a
>>different way than the implementation data model (aka physical model),
>>we have views. Although we put our base relations into nth normal
>>form, we don't have such rules for the view.
>>
>>Since my interest is in the interface between developer and dbms, the
>>view might be the area where the RM would have me focus (ignoring
>>practical issues in working with views such as performance issues).
>>
>>IF I am writing a s/w app with a browser user interface showing and
>>accepting data values that are laid out in a particular order on the
>>screen, each with a label, then it might make sense to write a view
>>that matches this web page. I could write a view of the data that
>>joins, projects and restricts so it includes the desired.
>>
>>Does this view need to be in 5NF? No. 4NF? No. BCNF? No. 2NF? No. 1NF?
>>Yes.
>>
>>That's where I get messed up because instead of just showing the view,
>>I have to massage that view simply because one of the attributes on the
>>page has cardinality greater than 1.
>>
>>If the view is supposed to be the view of the data, then why do we have
>>this 1NF restriction when we don't care about the other NF's in a view?
>>
>>Thanks in advance for your help. --dawn
>
>
I don't know if this is relevant to the subject but I gave some time ago an example of constructing a fairly complex query with repeating values in a column with Dataphor, a supposedly "true" RDBMS. This query could be contained in a view.
See http://www.orafaq.net/usenet/comp.databases.theory/2002/10/30/0482.htm
Note that this example uses an old version of Dataphor.
Regards,
Lauri Pietarinen
Received on Sat Jul 30 2005 - 09:34:01 CEST