在 SQL 中结合 FREQUENCY 计数和 INNER CASE

Question

对于超过 6 名学生的 class，我如何将两者结合起来以显示学生姓名 (sname) 和班级编号 (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

和

SELECT grade, 

COUNT(grade)AS Frequency

FROM enroll

GROUP BY grade

HAVING COUNT(grade)>6

Answer 1

看起来你们很亲密。我认为以下内容应该适合您：

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

在你的 2md Select 中，与 a class 没有关系，它有超过 6 个学生，恕我直言 GROUP BY 应该基于在像 classid 这样的列上。然后您可以使用 Windowed Aggregate:

简单地将两者结合起来

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

在 SQL 中结合 FREQUENCY 计数和 INNER CASE

Combining FREQUENCY count and INNER CASE in SQL

sql

frequency

inner-join

oracle-apex