在SQL中合并频率计数和INNER CASE

Question

如何组合两者以显示学生人数超过6的班级的学生姓名（sname）和部门编号（sectno）？到目前为止，我有这个

SELECT student.sname, enroll.sectno, 

FROM student 

INNER JOIN enroll 

ON student.sid=enroll.sid 

与

SELECT grade, 

COUNT(grade)AS Frequency 

FROM enroll 

GROUP BY grade 

HAVING COUNT(grade)>6 

Answer 1

看起来你是非常接近的。我认为以下应为你工作：

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

在你为2Md选择没有关系有超过6学生，恕我直言GROUP BY应根据柱像classid类。然后你就可以使用窗总结简单地结合两种：

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