> Yes, that seems like a good solution, Dimitry - though if there can be
> rows in 'b' that aren't in 'a' (admittedly, there were no such case in
> Maurizios example), 'coalesce(a.col1, b.col1) as col1' should be used
> rather than simply 'a.col1'.

Yes, if he urgently want to get zeros. But may be NULL is good enough
for him...

SY, SD.