Re: cdt glossary - TABLE
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Sun, 10 Jul 2005 15:21:22 +0200
Message-ID: <42d120d5$0$8315$e4fe514c_at_news.xs4all.nl>
>
>
> 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.
Date: Sun, 10 Jul 2005 15:21:22 +0200
Message-ID: <42d120d5$0$8315$e4fe514c_at_news.xs4all.nl>
Paul wrote:
> 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.
Lists are ordered by definition
(http://en.wikipedia.org/wiki/List), so
"the table header is an (unordered) set of column names"
directly contradicts
"the table header consists of a list of column names"
I don't have a problem listing contradictory definitions
if they are in use somewhere (in database context).
However, this is the first time I see a table header
with *un*ordered column names mentioned.
Are you sure? Could you provide some background?