Re: What databases have taught me

From: Bruno Desthuilliers <onurb_at_xiludom.gro>
Date: Sat, 24 Jun 2006 15:01:18 +0200
Message-ID: <449d37a0$0$20953$>

vc wrote:
> Bruno Desthuilliers wrote:
> [...]

>>. And all the litterature that keep on
>>saying RA can't do this.

> You are quite right that the RA (or the predicate logic of which the RA
> is a dialect) cannot express transitive closure.

Ok, so my teachers where not to blame then...

> It has to be extended
> with some kind of the TC operator.
> There is a standard (SQL'99) TC closure operator called 'recursive
> query'. Both DB2 and SQL Server 2005 have it. Oracle has had the
> proprietary 'connect by' since probably version 7. As far as I
> remember, Postgress used to have a patch that implemented the Oracle
> 'connect by'.

Well, so there's still some hope we will *one day* have something usable with a standard syntax, then ?

If I summarize all this, the problem with RM is not RM - it's RDBMS. Too bad we have to deal with RDBMS then.

bruno desthuilliers
python -c "print '_at_'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'onurb_at_xiludom.gro'.split('@')])"
Received on Sat Jun 24 2006 - 15:01:18 CEST

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