merge into ( select aa,bb,cc from table1) t1
using ( select aa,bb,cc from table2) t2
on (t1.aa=t2.aa)
WHEN MATCHED THEN
update set t1.bb=t2.bb;
merge into ( select aa,bb,cc from table1) t1
using ( select aa,bb,cc from table2) t2
on (t1.aa=t2.aa)
WHEN MATCHED THEN
update set t1.bb=t2.bb;