Re: Very simple question to relational theorists.

пятница, 4 мая 2012 г., 23:28:21 UTC+4 пользователь Bob Badour написал:
> On 5/4/2012 2:01 AM, Roy Hann wrote:
>
> Be careful: "some special rules" is handwavy enough that it could mean
>
> anything--including exposing physical details.

I'm not sure if this rule includes exposing physical details.

Suppose there are two normal relation in a system, which contain headers and lines of some documents (don't ask me about dots in front of name of attributes... I can name the attributes as I wish).

(1) DOC ( ID , .No , .Date , ...) //ID is pkey, No is a pkey too

and

(2) DOC.Lines ( ID , .Item , .Qty , ...) //Pair ID, Item is pkey.

I can create next virtual relation JOINed (1) and (2) by ID and RENAMEd sone attributes

(1+2) 'DOC(ID, .No, .Lines.Item , .Items,Qty)

At that all combinations (header_name + attribute_name) are the same in (1),(2) and (1+2) (...almost same ;), e.g. combination which gives name sequence Doc.Lines.Item. I keep a name sequences unchangeble.

This is my main rule.

Is such system relational?

I'm asking about this because it seems that I use reference constructions and all these dots seem to be the "physical details" you are speaking about. But in fact it's just play with names which is performed by RENAME operation. Received on Fri Aug 17 2012 - 17:37:23 CEST