HR: Multiple assignment records

Hi All,
I have requirement like, need to display multiple assignment and person records.

select pf.employee_number
,pf.full_name
,pf.email_address,
,paf.supervisor_id
,paf.job_id
from per_all_people_f pf
,per_all_assignments_f paf
where pf.person_id = paf.person_id
group by
pf.employee_number
,pf.full_name
,pf.email_address,
,paf.supervisor_id
,paf.job_id
having count(*)>=1;

I need to display multiple assignment records as well as person records. But above query taking too much time.
kindly explainme how to modify the query.

for ex: 1234 as employee number exists in application.