adding "order by" to a "group by" query

Hi,

This query:

select p.id_person, person_name(p), array_accum(distinct pt.type_fr)
from person p
left join person_to_event x using (id_person)
left join person_type pt using (id_person_type)
where person_name(p) ilike '%will%'
group by p.id_person,person_name(p);

returns:

id_person | person_name | array_accum
-----------+----------------------+-------------------------------
181 | William Eggleston | {comédien}
200 | William H.Macy | {comédien}
242 | William Nicholson | {auteur}
309 | William Friedkin | {réalisateur}
439 | William Shakespeare | {auteur}
591 | William Christie | {musicien}
786 | Paul Andrew Williams | {réalisateur}
1015 | William Mesguich | {comédien,"metteur en scène"}

But if I append this

order by pt.type_fr = 'comédien';

I get this error:

ERROR: column "pt.type_fr" must appear in the GROUP BY clause or be used in an aggregate function

It seems I am using pt.type_fr in an aggregate function (array_accum()),
yet I get the error.

Is there a way to to have a certain pt.type_fr bubble up (or down) in my
search?

Thanks,

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