Re: Database design

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Wed, 22 Feb 2006 01:12:15 +0100
Message-ID: <43fbac43$0$11074$e4fe514c_at_news.xs4all.nl>

Mark Johnson wrote:
> mAsterdam wrote:
>

>>>A relation is NOT a table
>>>An attribute is NOT a column
>>>A row is simply NOT a tuple, to the latter of course, I'd agree.

>

>>Not to the first two?

>
> Only because:
>

>>>A relation is a set, which need not be written as a table, to be sure.
>>>But in a world of constraints, situation and conditions - in a world a
>>>databases and a ng devoted to an aspect of same - I also agree it
>>>would be reasonable to speak of relations as tables, attributes as
>>>columns, and rows as not . . . entities.

I really do not understand what you are trying to say.

>>>>Yet, neither tables nor relations map to entity types.

>

>>>The single row is then called - what?

>

>>In the context of tables, just that: a row.
>>In the context of relations: a tuple.

>
> But, okay

?

>>>>One relation may have attributese from several entitiy types,

>
>

>>>Then an entity type is seen as some unique attribute domain? 

>
>

>>No. Why?

>
>
> And because a single table may have columns, each of which have
> different - types? What your definition of - entity? and "entity
> type"?

I don't think it is nice to snip a definition, then ask for it again, and ask for antoher one.

>>>>and one entity may have data spread across several relations

>

>>>Then an entity type is not some unique attribute domain?

>

>>Indeed not. Why should it?

>
>
> It appears definitional.

What is your definition of the relevant terms? Received on Wed Feb 22 2006 - 01:12:15 CET