错误"group function is nested too deeply"？

Question

尝试显示学生人数最少的部门的名称。

Answer 1

尝试这样的事情：

SELECT TOP 1 department_name, count(*) AS number_of_students
FROM department natural join student
GROUP BY department_name
ORDER BY number_of_students

它将为您提供按学生人数排序的部门列表。通过仅通过TOP 1选择第一行，您将只获得学生人数最少的部门。

Answer 2

是这样的吗？

SELECT 
T1.department_name, COUNT(T2.department_id) totalCount
FROM department T1
LEFT JOIN student T2
ON T1.department_id = T2.department_id
GROUP BY T2.department_id
HAVING COUNT(T2.department_id) =
(
  SELECT  
  COUNT(T2.department_id) totalCount
  FROM department T1
  LEFT JOIN student T2
  ON T1.department_id = T2.department_id
  GROUP BY T2.department_id
  ORDER BY totalCount ASC
  LIMIT 1
)

SQLFIDDLE 演示