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model inherited object

From: <deja_at_2bytes.co.uk>
Date: 21 Jun 2006 04:25:13 -0700
Message-ID: <1150889112.956952.209440@p79g2000cwp.googlegroups.com>


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?

TIA
Phil Received on Wed Jun 21 2006 - 06:25:13 CDT

Original text of this message

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