查询是否必须是此表单？

Question

书名：数据库系统概念/作者：Silberschatz，Korth，Sudarshan

问题：找出已经上过ID 10101教师授课的（不同）学生的总数

回答：

select count(distinct ID)
from takes 
where (course_id, sec_id, semester, year) in
          (select course_id, sec_id, semester, year
           from teaches 
           where teaches.ID = 10101
          );

我的疑问：

select count (distinct ID)
from takes 
where course_id in (SELECT course_id from teaches where teaches.ID = 10101);

我必须是正确答案吗？