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Re: What databases have taught me

From: Marshall <marshall.spight_at_gmail.com>
Date: 23 Jun 2006 20:19:52 -0700
Message-ID: <1151119192.387319.235660@r2g2000cwb.googlegroups.com>


Bob Badour wrote:
> Marshall wrote:
>
> > Bob Badour wrote:
> >
> >>Would (R AND x = 1 AND y = 2) = (x = 1 AND y = 2 AND R) ?
> >
> > I'd think it would have to, wouldn't it? Assuming = binds with
> > higher precedence than AND in the above syntax, and assuming
> > AND is associative and commutative, which I would hope it
> > would be. It is in the Tropashko algebra.
> >
> >
> >>If so, wouldn't that make name resolution kinda complicated and perhaps
> >>error-prone?
> >
> > I don't see any obvious complications to name resolution, but then
> > I might be mising what you're getting at.
>
> How will the dbms know when a name refers to an attribute vs a relation
> variable?
>
> Consider:
>
> R AND x = y
>
> What if the dbms has relvars x and y and R has attributes x and y?

Ah, I see what you're saying now. Yes, that could well be an issue. I'm not familiar enough with this syntax to say much.

> > As to error-prone,
> > (assuming we are talking about the progammer writing the
> > above code) yes, it might be, especially at first. I would
> > expect to address that issue with coding conventions and
> > possibly syntactic support. It's hard to say how much of
> > an issue that will be without field experiece. (Which I don't
> > have with this question.)
>
> Okay, as long as we are not talking about the language the programmer
> works in, one can handle name resolution syntactically in the
> human-readable language and use something unambiguous internally.

Yes. Again, I'm not much familiar with the above syntax, but I could well imagine some challenges cropping up, given the lack of any marker characters and the (multiple?) uses of '='.

Marshall Received on Fri Jun 23 2006 - 22:19:52 CDT

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