mysql - 如何编写平均 innerQuery

Question

从图像中我有相同的类(class) ID 和多个视频，因为我想将整体观看百分比显示为它们的平均值我该怎么做我想要这样的东西:

(SELECT SUM(watched_percentage) FROM tbl_student_learning_path where course_id = 298 
AND SELECT COUNT(watched_percentage) FROM tbl_student_learning_path where course_id = 298)
as overallScore 

Answer 1

根据评论，您可以通过这种方式获得加权平均值

SELECT
    course_id,
    (100 * SUM(watched_total_time) / SUM(video_total_time)) AS WeightedAvg
FROM
    tbl_student_learning_path 
WHERE
    course_id=298
GROUP BY
    course_id