drop view teacher_v;
create view teacher_v as
	select
		t.code as 番号,
		t.name as 名前,
		s.name as 教科,
		(select count(*) from assign where t.code = t_code) as 受講人数
	from teacher t
	join subject s on t.s_code = s.code
	order by t.code
;