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Re: model inherited object

From: <deja_at_2bytes.co.uk>
Date: 21 Jun 2006 12:58:28 -0700
Message-ID: <1150919908.735143.249850@y41g2000cwy.googlegroups.com>


hi bob,

> post is a crank. That said, I suggest the first step toward a solution
> might be to avoid the First Great Blunder.

I have just started reading about First Great Blunder ie class = table, row = object is wrong, which is obviously my design. Though I am somewhat restricted by the current solution, being new to this whole "Blunder" thing - any pointers on how it would be best to model this scenario avoiding this blunder.

TIA Bob Badour wrote:
> deja_at_2bytes.co.uk wrote:
>
> > sorry - crossposting (from sqlserver programming) as it's more likely
> > to be relevant here
> >
> > I have a table which I have previously used for objects of a certain
> > class i.e.
> >
> > book
> >
> > this table has a number of columns representing the properties of the
> > book i.e number of pages, author etc.
> >
> > I want to be able to record an inherited object so for example I will
> > have Book1_v1 and Book1_v2 - the only difference between them being the
> > number of pages and the title. However Book1_v3 might be inherited from
> > Book1_v2 but with a different title only while Book1_v4 might be the
> > same as Book1_v3 but with a different publication date.
> >
> > If I copy the Book1_v1 to a new record for Book1_v2 and change the
> > number of pages, if I then change the author of Book1_v1, it will not
> > be reflected in Book1_v2 (and it would be difficult to do via triggers
> > because you cannot be certain which fields are "overridden").
> >
> > Even if I have a table that says [BookId, version number, property,
> > value] to override any number of properties then I am still going to
> > end up with horrible joins and datatype issues and working my way back
> > from v4 to v1 to get a complete row would be a nightmare.
> >
> > What is the solution?
>
> Anyone who tells you they have a solution based on a sketchy newgroup
> post is a crank. That said, I suggest the first step toward a solution
> might be to avoid the First Great Blunder.
Received on Wed Jun 21 2006 - 14:58:28 CDT

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