MERGE statement is that you need:
http://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_9016.htm#SQLRF01606
SQL> select * from t;
ID N
---- -
1 a
SQL> select * from t1;
ID NA
---- --
1 a1
2 b1
SQL> merge into t using t1 on (t.id = t1.id)
2 when matched then
3 update set t.name = t1.name
4 when not matched then
5 insert (t.id, t.name) values(t1.id, t1.name)
6 /
2 rows merged.
SQL> select * from t;
ID NA
---- --
1 a1
2 b1