您可以在college字段和其他student上使用self-left连接，只返回那些不匹配的记录：

select t1.college from yourtable t1
left join yourtable t2 on t1.collage=t2.college and t1.student<>t2.student
where t2.college is null

假设没有严格的副本，可以使用 not exists 看看学校里还有没有其他学生：

select t.college
from t
where not exists (select 1
                  from t t2
                  where t2.college = t.college and t2.student <> t.student
                 );

不使用的限制 count 听起来有点做作，但假设 student 以及 college 是唯一的，您可以比较每个学院的最大值和最小值，并确保它们是同一个学生：

SELECT   college
FROM     mytable
GROUP BY college
HAVING   MIN(student) = MAX(student)

你可以用 LAG() 以及 LEAD() ，例如：

select
    *,
    lag(college) over(order by college) as prev_college
    lead(college) over(order by college) as next_college
  from my_table
  where college <> prev_college or prev_college is null
    and college <> next_college or next_college is null