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select employee_id as id, job_id, last_name, to_date(sysdate) from employees union select employee_id, job_id, to_char(null), to_date(end_date) from job_history order by 1,3,4 desc
select first_name, last_name from employees where employee_id in ( select employee_id from employees where job_id = 'IT_PROG' union select employee_id from job_history where job_id = 'IT_PROG' ) ------ select first_name, last_name, stand, datum from employees, ( select employee_id, job_id, 'jetzt' stand, sysdate datum from employees where job_id = 'IT_PROG' union select employee_id, job_id, 'früher' stand, end_date datum from job_history where job_id = 'IT_PROG' ) history where history.employee_id = employees.employee_id