Re: Why all the max length constraints?

dawn wrote:
> Tony D wrote:
> > given that the premise it starts from is thoroughly discounted in at
> > least one of the books Dawn claims to have read,
>
> I read 'em, but didn't memorize 'em, feel free to point me to a page
> number that answers my question.

There is no such page, apparently. You have said elsewhere in this thread that you know that:

> > "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*."

You said:

> That I know. That does not answer my question.

So it is clear that you DO know that there is nothing in RM that would require a DBMS to implement length constraints on attributes, yet you continue to deny that you know it.

Your question seems to boil down to: why *can* you constraint the length of strings in a SQL DBMS but you *can't* in an MV DBMS?

It seems a bit like asking "why does car X offer climate control while car Y doesn't? What is it about car X that makes it /need/ climate control while car Y doesn't".

Your serif / sans-serif analogy doesn't make sense either. SQL DBMSs don't impose length constraints on columns "by default". In each and every case the constraint is specified by the person creating the table. If it did impose them by default then presumably columns would tend to all have the same length constraint, e.g. 50, whereas a cursory glance at a typical database shows lots of different length constraints being used. Received on Mon May 29 2006 - 11:37:30 CEST