merge into 있으면 update, 없으면 insert

merge into tb_a a
 using dual
     on (a.code = ?)
 when matched then
          update set name = '있다'
 when not matched then
          insert (code, name) values (?, '없다')


merge into tb_aaa a
 using (select code, name tb_bbb where code=?) b
     on (a.code = b.code) 
 when matched then
          update set a.name = b.namel
 when not matched then
          insert (a.code, a.name ) values (b.code, b.namel );