oracle merge的用法

select * from test;
select * from test2;

merge into test a
using test2 b
on (a.id = b.id)
when matched then
  update set a.height = b.height,
             a.teleph = b.tel;
--  when not matched then

update test set height = (select t2.height from test2 t2 ,test t1 where t2.id = t1.id and t1.id=3)
where id = 3

update test set height =null