Posted by Jerry Stuckle on 05/15/06 03:57

Kenneth Downs wrote:
> Bent Stigsen wrote:
>
>
>>
>>The answer is D, implementing two tables.
>>One table with the characteristics, and one table containing two foreign
>>keys making the association between characteristics and the "items" (what
>>that might be).
>
>
> Anybody working with databases must have a reasonable method for altering
> table structures as a regular event and a reasonable way to synchronize
> structures and the code that works with them. Not having this will cost,
> and all solutions that seek to re-invent physical implementation produce
> burdens worse than the disease.
>

I disagree. If you properly plan your installation, you will not need to change
your tables. Over the years I've designed hundreds of databases; most of them
have never been changed.

Having to alter a database layout either means you've had a significant change
in the database needs, or, more likely, you didn't design it properly in the
first place.

> The solution you present may be correct in his case, but it verges on the
> dreaded 'abstraction' of the E-A-V system, and if that is so it would be a
> cure worse than the disease. Whether it is a valid cross-reference or an
> instance of E-A-V would require knowing more about the system.
>

Not at all. In fact, it makes things much easier to handle in the long run.
When you have a multi-to-multi connections, as in this case, a third table is
almost always the way to go.


> But I would repeat that any 'abstraction' made in an attempt to avoid table
> structure changes is going to fail. It fails because you give up what the
> server can do for you and end up spending your time reinventing an RDMBS
> server.
>
>

I completely disagree. Again, many times I've abstracted things yet made good
use of the server's abilities.

Abstraction only means you're separating the database structure from the program
logic. This is generally considered a good thing, especially as you get into
more complicated projects..



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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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