Path: dp-news.maxwell.syr.edu!spool.maxwell.syr.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!postnews.google.com!y43g2000cwc.googlegroups.com!not-for-mail
From: "Tony Andrews" <andrewst@onetel.com>
Newsgroups: comp.databases.theory
Subject: Re: Why all the max length constraints?
Date: 29 May 2006 02:37:30 -0700
Organization: http://groups.google.com
Lines: 38
Message-ID: <1148895450.644963.316800@y43g2000cwc.googlegroups.com>
References: <1148773922.267863.170930@j55g2000cwa.googlegroups.com>
   <RX5eg.41165$mh.17709@tornado.ohiordc.rr.com>
   <1148779920.250512.318140@j55g2000cwa.googlegroups.com>
   <Rv7eg.41177$mh.17895@tornado.ohiordc.rr.com>
   <1148787091.347602.244980@j55g2000cwa.googlegroups.com>
   <1148803338.207150.215910@g10g2000cwb.googlegroups.com>
   <1148830139.977178.20070@u72g2000cwu.googlegroups.com>
   <1148836298.990128.155960@g10g2000cwb.googlegroups.com>
NNTP-Posting-Host: 80.3.32.7
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
X-Trace: posting.google.com 1148895456 29146 127.0.0.1 (29 May 2006 09:37:36 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Mon, 29 May 2006 09:37:36 +0000 (UTC)
In-Reply-To: <1148836298.990128.155960@g10g2000cwb.googlegroups.com>
User-Agent: G2/0.2
X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.8.0.3) Gecko/20060426 Firefox/1.5.0.3,gzip(gfe),gzip(gfe)
X-HTTP-Via: HTTP/1.1 ntl_site[50032007] (Traffic-Server/5.2.4-59380 [uScM])
Complaints-To: groups-abuse@google.com
Injection-Info: y43g2000cwc.googlegroups.com; posting-host=80.3.32.7;
   posting-account=IJrbaQwAAACC57cNvnaNWPkLUkH3QWCJ
Xref: dp-news.maxwell.syr.edu comp.databases.theory:40186

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.