在SQL中合併頻率計數和INNER CASE

Question

如何組合兩者以顯示學生人數超過6的班級的學生姓名（sname）和部門編號（sectno）？到目前爲止，我有這個

SELECT student.sname, enroll.sectno, 

FROM student 

INNER JOIN enroll 

ON student.sid=enroll.sid 

與

SELECT grade, 

COUNT(grade)AS Frequency 

FROM enroll 

GROUP BY grade 

HAVING COUNT(grade)>6 

Answer 1

看起來你是非常接近的。我認爲以下應爲你工作：

SELECT 
student.sname, 
enroll.sectno, 
COUNT(enroll.grade) AS Frequency 
FROM student 
INNER JOIN enroll ON student.sid=enroll.sid 
GROUP BY student.sname, enroll.sectno 
HAVING COUNT(enroll.grade)>6 

Answer 2

在你爲2Md選擇沒有關係有超過6學生，恕我直言GROUP BY應根據柱像classid類。然後你就可以使用窗總結簡單地結合兩種：

with cte as 
(
    SELECT student.sname, enroll.sectno, 
     -- get the count per class, might be a different column than sectno 
     count(*) over (partition by enroll.sectno) as cnt 
    FROM student 
    INNER JOIN enroll 
    ON student.sid=enroll.sid 
) 
select * from cte 
where cnt > 6