HR 스키마에서 job_history가 있는 사람은 Y를 붙여서 출력하는 sql문

create or replace view v_emp_job_history as
select  distinct a.*, decode(b.employee_id, null, null, 'Y') history
from    employees a, job_history b
where   a.employee_id = b.employee_id(+);