Re: Join syntax and join orde

Tom Lane wrote:
> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
>
>>Can we make the fact that the "explicit" inner join syntax also controls
>>the join order optional?
>
>
> I'm certainly not wedded to it, but what's the implementation plan,
> and how will you make the control available to them that needs it?

How do you do it now with the non-standard syntax? You can get some
control by use of subselects. In Oracle we use this trick in some cases
because it has the nasty habit of applying PL/SQL functions to all rows
of a relationship *before* qualification.

The problem with the current situtation is that someone who writes a
standard SQL92 query mixing inner and outer joins gets the benefit of
optimizer decisions in Oracle 9i and other commercial databases that
supports the syntax, but not PostgreSQL.

For those of us who write applications designed to work on multiple
RDBMSs this poses something of a problem. In our case not much of a
current one because we still support Oracle 8i which doesn't have SQL92
join syntax, so we're forced to write different outer join queries for
it and PG anyway. But eventually we'll drop Oracle 8i support and look
to share queries, at least for new code.

--
Don Baccus
Portland, OR
http://donb.photo.net, http://birdnotes.net, http://openacs.org