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Re: cdt glossary - TABLE

From: Paul <paul_at_test.com>
Date: Sun, 10 Jul 2005 13:28:33 +0100
Message-ID: <42d1146f$0$24152$ed2619ec_at_ptn-nntp-reader02.plus.net> 






mAsterdam wrote:

>> A *table* consists of a table header and a body. The *table header*
>> consists of a list of column names that contains each column name at
>> most once and associates with each column name in that list a certain
>> type. The *body* is a bag of rows where a *row* is a list of values
>> that conforms to the table header.




> 

> The bag you speak of is not a mixed bag.


> Just the "unorderedness" of bag is crucial here, right?

> 

> Another thing bugging me is: every representation of

> a table /has/ order - but the tables we speak about

> have none - or do we pretend they have none?

> I would apreciate it if we would have a friendly explanation

> for that - it confuses anyone when starting to think about

> tables at first.




You could say the table header is an (unordered) set of column names.



And the rows are (unordered) sets of (column_name, value) tuples such
that there is the obvious 1-1 mapping between the members of each row
and the table header.



I think I've seen this description somewhere and it gets round the
problem of column order. Though possibly it makes the description more
complicated for newbies.



Paul.
Received on Sun Jul 10 2005 - 14:28:33 CEST












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