Re: Pizza Example

From: Dawn M. Wolthuis <>
Date: Wed, 7 Apr 2004 11:04:23 -0500
Message-ID: <c518r5$lqk$>

> Over what other operations are Pick data structures closed? Or rather,
> Pick operations are closed over its data structures?

Eric -- because there is no such formalization of the PICK structures as there is with relational ones, I'm being very imprecise here to the extent that I would call this an eyeballing feature -- if you write a SQL statement and see the output on the screen, the output is 2D and includes repeating data.


might yield

Davy Jones Philosophy
Davy Jones Mathematics

There is no base table that is modeled with the name "Davy Jones" stored in it twice, but a query on the view yields this output.

PICK idenfies whether data is physically stored or is virtually-defined at the field level, not the table/file level. So, all descriptions of a file are "views". Queries on these yield results that look just like base tables. The user just asks for fields from a given file -- the data could come from anywhere (which is why I call the file descriptions views -- they would not be considered such from a SQL standpoint). If you ask for the same data from a PICK file that we requested above you might ask: LIST STUDENTS NAME MAJORS to get

Davy Jones Philosophy


The output looks like one record, just as the input for this information was one entry from the end-user perspective. Obviously one can do gyrations and have output from a relational database imitate the natural PICK way of doing things, but it is not the natural way that SQL/relational databases handle data.

This is just that 1NF thing cropping up again. It seems like such a minor point and yet it can really make a significant difference in how easy it is to establish and maintain data. --dawn Received on Wed Apr 07 2004 - 18:04:23 CEST

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