Re: Perhaps an idiotic question

From: Neo <>
Date: 29 Nov 2006 18:46:06 -0800
Message-ID: <>

> > First, to make the declaration, your language has to make some sort of
> > forward reference to the type. Second, to have this exactly as stated
> > yields a potentially infinite progression of the type. In practical
> > terms, one would have to settle for a finite recursion because computers
> > are finite machines. ie. If one serially ungroups the A attribute, at
> > some finite step, ungrouping would yield an empty relation with
> > cardinality zero.
> Thanks for that. I agree about the forward reference but it seems
> non-controversial, eg., not uncommon, to me and as well about the
> infiniteness (which might be the aspect that intrigued me). As for the
> infiniteness, I don't want to distract into what's practical and what's
> not except to say that we sometimes ignore infinite issues in practice,
> given enough memory we are sometimes prepared to let things 'fall apart'
> at some point, eg., crash/fail as long as we never get a wrong answer
> for the progressions we can handle.

I think you are saying, since a table is defined after its columns are defined, this leads to a catch-22 situation if a column needs to reference the table it is in which hasn't been defined yet. Would one way around this be, to create the table without the column and then add it later? Received on Thu Nov 30 2006 - 03:46:06 CET

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