create or remplace function getMoyQuantiteClient(un_ncli clients ncli%type)
returns decimal(10.2) As
$$
	declare
		moy decimal(10.2);
	Begin
		Select AVG(qa) into moy from achat
		where ncli = un_ncli;
		return moy;
	end
$$ language plpgsql;
-- select getMoyQuantiteClient(101);