查找具有最高登记的类的名称

Question

我在数据库中有以下关系

ENROLLMENT (snum: int, cname:varchar(100))

其中snum是学生ID，cname是课程名称

我希望找到注册人数最多的班级名称。

Answer 1

有多种解决方案。一种解决方案是使用SELECT TOP 1：

SELECT TOP 1 
    cname, count(*) as NumberOfStudents
FROM ENROLLMENT
GROUP BY cname
ORDER BY count(*) desc

Answer 2

使用公用表表达式（cte）：

with cte as
(
  select cname, count(*) as cnt
  from ENROLLMENT
  group by cname
)
select cname
from cte
where cnt = (select max(cnt) from cte)