Подскажите что не правильно в Union.

Select Flight_Data.Log_page,
Employee_name = Last_name + " " + First_name,
flight_Data.upd_timestamp,
audit_employee_oid

from Flight_data, employee_data
where flight_data.audit_employee_oid = employee_data.oid and
employee_Data.oid = :empl_oid

Union

select log_age = " ",
Employee_name = Last_name + " " + First_name,
upd_timestamp = " ",
signed_for_mech_oid
from work_order_data, employee_data
where work_order_data.signed_for_mech_oid = employee_data.oid and
employee_Data.oid = :empl_oid

Nuzhno soedinit' records iz pervoi i vtoroi query