Re: SQL compatibility reminder: MySQL vs PostgreSQL

Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I think the new item might be phrased a little too broadly.  The
> problem with mysql's GROUP BY behavior is not the syntax but the
> nonstandard semantics, ie, that it will pick a random result row
> when the query is underspecified.
I thought that some of the items on the OP's list were requests to
add an alternative syntax for an existing feature, without a change
in semantics.  Did I misunderstand that?  If not, is it something we
want to consider?
I do know that some of the requests were to support behavior we
would consider incorrect (like the non-deterministic results from an
underspecified GROUP BY); not only do we not want to go to any
effort to *add* it, but we'd probably be putting in effort to
*eliminate* it if it was present.  Should the TODO list "not wanted"
section explicitly list each such feature, so that non-listed
features aren't painted by the same broad brush?
> I believe what that's actually about is the idea of converting
> things like Oracle's CONNECT BY into SQL-spec constructs.  Doing
> so wouldn't break any existing PG-compatible applications, whereas
> messing with the semantics of GROUP BY probably would.
Yeah, my first draft of that was even broader, not naming MySQL in
particular -- but then I remembered that we've made a few
concessions to Oracle compatibility.  As far as I can recall,
though, those tend not to involve new syntax, but functions that
aren't required by the standard -- which seems much less invasive
than the OP's requests.
I'm willing to rework, soften, or narrow the entry as needed, and I
certainly would take no offense at anyone else doing so.  I was just
trying to get it listed, since there seemed to be some community
consensus on the point.
-Kevin