procedure add_json
----------------------------------
(
	p_check			out	varchar2,
	p_json			in	varchar2
)
is
begin
	if p_json is JSON then
		select json_query(p_json.username, 'p_json') into p_check;

	else
		p_check := 'This is not JSON';
	end if;
end;

{ username: 'Иван', email: 'test@test.ru', phone: '78982482244' }