Re: Why all the max length constraints?

Tony D wrote:
> Yes, it is a rather silly question. It's an almost impressively silly
> question because if, as you've mentioned elsewhere, you've read TTM,
> you should have seen stated in several different ways the assertion
> that the relational model is orthogonal to the type system. A quick
> Google found an interview (http://www.dbmsmag.com/int9410.html)
> discussing an earlier version of the book, where Date says :
>
> "The reason I say the ideas of object-oriented (at least the good ones)
> are orthogonal to the ideas of the relational model is that *nowhere
> does the relational model prescribe what data types you have*."

That I know. That does not answer my question. I fully understand that one need not specify max length constraints if implementing only "in theory." I wondered if there were anything in the theory that might prompt implementations that have, perhaps as a side-effect, the need for or advantage when individual attributes are specified with max length constraints. That is not at all the same question as whether such the theory says that the implementations must have such a feature.

> Unless the subtext was to have another tussle over the old "what's a
> scalar type ?" question ...

By no means.

> If you're asking "why do (at least the majority) of SQL databases
> require length constraints", then it's very probably to do with the way
> those products chose to represent tables on disk.

Yes.

> There may also be
> "bleed" from other language designs into SQL

Yes. mAsterdam's serif analogy might be applied to the physical implementations as well as the feature sets.

It hesitate to report that I still don't know the answer to my question, but I will research it differently and see if I can get further. It actually thought it would have a simple answer and that someone would have that answer handy enough to pass it along, but it seems you and others misinterpreted the question. I wish I knew why, but I'm starting to suspect that others do not have a framework in which they could easily understand my actual questions. I'm starting to see that those who understand my questions are the ones who do not get angry with me.

If you have any interest in doing me a favor, Tony, I would really, really appreciate it if you could try to understand what I am asking and let me know if you are getting closer to understanding that. It is no doubt an ignorant question but I'm quite sure it is not a stupid question. Let me know if you are getting any closer to seeing that.

Thanks. --dawn Received on Mon May 29 2006 - 04:28:16 CEST