Re: Why lower's not accept an AS declaration ?

On Tue, 19 Aug 2003, Tom Lane wrote:

> I said:
> > After reading over the spec again I finally realized the significance of
> > this bit:
>
> >               i) Let X be any <column reference> directly contained in K(i).
> >              ii) If X does not contain an explicit <table or query name> or
> >                  <correlation name>, then K(i) shall be a <column name> that
> >                  shall be equivalent to the name of exactly one column of
> >                  ST.
>
> Wait a second ... this is a classic case of reading what you expected
> rather than what's there.  I thought that (ii) said "If X does not ...
> then X shall be ..." but that's not what it says --- the "then" says
> that the whole sort-key K(i) must be an output-column name.

Err, yeah.  That's certainly different than reading that as then X shall
be. :(

> In other words, SQL99 does not allow expressions over output-column
> names.  An output-column reference can only appear as a simple name
> (same as SQL92, and same as what we allow).  SQL99 allows expressions
> over input-column names ... but only if the expressions use
> fully-qualified input-column names.
>
> This last is such a stupid restriction that I can't believe I'm reading
> it right; is it just too late at night for me?

Yeah.  These rules don't seem to make much sense, why bother making
it a general value expression if you're going to limit it like that?
It almost makes me wonder what SQL200x is going to do to the clause.

How about we forget that I ever brought it up. ;)