MySql - 加入并计算记录中的数据

Question

我尝试按用户ID计算数据记录，但结果是总行记录，我有下面的数据 enter image description here

我在这里使用查询：

＆＃13;

＆＃13;

SELECT user.id, COUNT(upload.user_id), upload.file_name FROM upload Right JOIN user ON upload.user_id = user.id;

＆＃13;

＆＃13;

＆＃13;

Answer 1

如果您想按user_id计算，那么您根本不需要JOIN，它可以是一个简单GROUP BY COUNT，例如：

SELECT user_id, COUNT(*)
FROM upload
GROUP BY user_id;

Answer 2

我会这样做SELECT us.id, (select count(*) from upload where user_id=us.id), u.file_name FROM upload u, user us where u.user_id = us.id;