Update table1 set key1 = (select key2 from table2 where table2.key2=table1.key1) where exists (select key2 from table2 where table2.key2=table1.key1)
update table1 a set a.column1=( select column2 from table2 b where a.key1=b.key2)
Update table1 set key1 = (select key2 from table2 where table2.key2=table1.key1) where exists (select key2 from table2 where table2.key2=table1.key1)
update table1 a set a.column1=( select column2 from table2 b where a.key1=b.key2)