问题描述
我有一个数据库，我想创建一个带有COUNT函数的表。是否有可能？
I have a database and I want to create a table with COUNT function in it. Is it possible ?
我有3个现有的表：
Member
Feedback
Attendance
在反馈表中，2列
Class_ID,
Likes
（Class_ID与考勤链接，每个成员参加1班，例如班1,2,3等，Likes是班上的人数）。
(Class_ID link with the attendance, as each member attend 1 class eg. class 1,2,3,etc. and Likes is for the number of people like the class).
在考勤表中，3列：
Class_ID
Member_ID
Non_member_name
现在我想更改反馈表以添加2个新列。一个计数参加类的人数，例如，如果有4个人参加类1，将有4行Class_ID = 1。两个计数喜欢的百分比，即喜欢/数量_attending * 100％
Now I want to alter Feedback table to add 2 new columns. One to count the number of people attend the class, e.g if there is 4 people attend class 1,there would be 4 rows of Class_ID=1. Two to count the percentage of likes i.e Likes/Number_attending*100%
ALTER TABLE Feedback
ADD COUNT(*) AS Number_Attending
WHERE Class_ID.Feedback=Class_ID.Attendance
我试图运行，但有
推荐答案
例如：
SELECT Class_ID, Count(Member_ID) As MemCount, Count(Non_Member_Name) As NonMemCount
FROM Attendances
GROUP BY Class_ID
请参阅
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