Обсуждение: Re: PostgreSQL SQL92: CORRESPONDING BY

I received this via private email.  Do we want CORRESPONDING added to
the TODO list?

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David H. Johnson wrote:
> Hi,
> 
> I am writing you because you're listed as the TODO List maintainer.  I noticed
> that PostgreSQL does not support the CORRESPONDING BY clause for
> UNION/INTERSECT/EXCEPT.  The only reference I have found to this functionality
> in the mailing list archives is this message by Tom Lane:
> 
> http://fts.postgresql.org/db/mw/msg.html?mid=1273164
> 
> In the message he discusses a rewrite of UNION/INTERSECT/EXCEPT for PostgreSQL
> 7.1 to allow them to work with views and subselects.  Tom also says that he
> will not try to implement the CORRESPONDING option, but that it should be a
> fairly straightforward extension when it is attempted.
> 
> I was wondering if you (or the PostgreSQL development team) would consider
> adding the CORRESPONDING option of UNION/INTERSECT/EXCEPT queries to the TODO
> list.
> 
> Thanks for reading.
> 
> --David
> 
> -- 
> David H. Johnson, Engineer I
> University of Alabama at Birmingham
> Center for Biophysical Sciences and Engineering
> 
> E-mail:    dhj@uab.edu
> Phone:    (205)934-6759
> Fax:    (205)934-0480
> 

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> I received this via private email.  Do we want CORRESPONDING added to
> the TODO list?

Sure. Though since we now have features.sgml which has the complete set
of SQL99 itemized features we perhaps should shrink the ToDo entries
regarding SQL99 features to only one:

"Support additional SQL99 features"

Anything more specific which does not itemize all the features which we
might want to see implemented probably does not help. And carrying the
list in two places is more trouble than it is worth imho.

I've been working on separating the current single list of features into
"Supported" and "Unsupported" lists; will commit a first cut this
evening. Look in
 http://developer.postgresql.org/docs/postgres/features.html

for the most recent version available. I estimate that we have about two
thirds of the feature set implemented. I'm looking at implementing some
of them as (almost) trivial improvements or changes to our syntax; I've
got CREATE CAST... as one of the first ones to do.
                     - Thomas