It seems to me that it has always been implicitly assumed around here
that the MERGE command would be a substitute for a MySQL-like REPLACE
functionality. After rereading the spec it seems that this is not the
case. MERGE always operates on two different tables, which REPLACE
doesn't do.
That said, what kind of support for insert-or-update-this-row do we want
to provide, if any? Should it be a REPLACE command, an extension of
the INSERT command, a modication of the MERGE syntax, or something
else?
--
Peter Eisentraut
http://developer.postgresql.org/~petere/