try:
update emp
set emp.emp_name = (select max(employee.name) from employee
where employee.id = emp.emp_id)
where exists(select employee.name from employee
where employee.id = emp.emp_id)
update emp
set emp.emp_name = (select max(employee.name) from employee
where employee.id = emp.emp_id)
where exists(select employee.name from employee
where employee.id = emp.emp_id)
update emp
set emp.emp_name = (select max(employee.name) from employee
where employee.id = emp.emp_id)
where exists(select employee.name from employee
where employee.id = emp.emp_id)
using employee e
on (em.emp_id = e.id)
when matched then
update set em.emp_name = e.name
when not matched then
insert values(e.id,e.name);