Bryce Nesbitt <bryce1(at)obviously(dot)com> writes:
> If it were for the same rows in the same table, I would not have asked.
> This is for columns from two tables, whos relationship is only
> meaningful after a join.
You have to write out the join condition longhand, eg
UPDATE targettable SET targcol = srccol
FROM srctable
WHERE joincol1 = joincol2;
This can be tricky, particularly if there might be more than one source
row joining to a given target row. (IIRC, the effective behavior is
that any given target row's update will occur against a random one of
the possible join partners.) A lot of people prefer to code it using
sub-selects.
regards, tom lane