SQL - 从查询中作为单个数字获取答案

Question

以下代码返回一对数字，标识参与三个以上活动的人员。

SELECT pnr 
FROM Participates 
GROUP BY pnr 
HAVING count(activities)>3; 

我希望答案是参加超过三个活动的人数，即“4”，而不是四个唯一的数字。该怎么办？

Answer 1

Access支持派生表。

SELECT COUNT(*) AS NumberOfParticipants FROM 
(
SELECT pnr 
    FROM Participates 
GROUP BY pnr 
HAVING count(activities)>3 
) T 

Answer 2

您需要在pnr领域的WHERE子句来唯一地标识您的分组之一：

SELECT COUNT(pnr) 
FROM Participates 
GROUP BY pnr 
WHERE pnr = 'whatever' 
HAVING COUNT(activities)>3 

我的条款的顺序可能是错误

Answer 3

Select Count(Distinct pnr) 
From Participates 
Having Count(activities) > 3