Re: SQL92 compliance

On Wed, 2006-08-23 at 12:40, Tom Lane wrote:
> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> > Am Mittwoch, 23. August 2006 03:40 schrieb Daniel CAUNE:
> >> Is AS in "SELECT my_column AS my_name FROM my_table" mandatory to be SQL92
> >> compliant?
>
> > No. I have a patch at
> > <http://developer.postgresql.org/~petere/select-without-as/select-without-as.patch>
> > that fixes this at least for 7.4.
>
> I think it's a big stretch to say that that patch fixes it, since it
> only allows an AS-less target expression to be c_expr rather than
> a_expr as it ought to.
>
> The problem is really insoluble given that we allow user-defined
> postfix operators: is "SELECT x ~~ y" meant to be an infix operator
> with arguments x and y, or a postfix operator with argument x and
> a column label y?
>
> When this has come up in the past, we've always concluded that
> compliance with this not-very-well-thought-out detail of the spec
> is not worth the price of giving up postfix operators.
>
> Even if we were willing to do that, I think we'd also have to give
> up using bison to generate the parser :-( because some constructs
> would require more than one-token lookahead.

Would it be possible if we required postfix operators and related to be
inside parens?

select x ~~ y as yabba
OR
select (x ~~ y) yabba

Not that I'd want that. I prefer it the way it is too. Just more of an
intellectual exercise.