Question

除了Get total sum of video comments for each video之外，我还注意到无法使用v.commentCount，因为我清除了一些数据，但现在该列不准确。

所以我需要在评论表中计算videoId评论和所有videoID评论。

我有台视频

videoId | channelId
a       | 1        
b       | 1        
c       | 2
d       | 2

和一个表注释。 video.channelId映射到comment.videoID_channelID

   commentID | replyID | videoID | videoID_channelID | textOriginal
   c1        | NULL    | a       | 1                 | "test"
   c2        | NULL    | a       | 1                 | "some text"
   NULL      | r1.c1   | b       | 1                 | "asdad"
   NULL      | r2.c1   | b       | 1                 | "xxx"
   c5        | NULL    | b       | 1                 | "yyy"
   c6        | NULL    | c       | 2                 | "zzz"
   c7        | NULL    | d       | 2                 | "-...-."

对于每个videoId，我都需要commentCount（每个videoId有多少条评论）以及该频道的所有commentCounts的总和（对于channelID的每个视频有多少总评论？）。

所以最终结果应该是：

videoId | channelId | commentCount | commentCount_sum
a       | 1         | 2            | 5
b       | 1         | 3            | 5
c       | 2         | 1            | 2
d       | 2         | 1            | 2

到目前为止，我的代码：

SELECT v.videoId,
        v.channelId,,,
        count(c.textOriginal) commentCount,
        count(c.textOriginal) over (partition by c.videoID_channelID) as commentCount_sum,
FROM videos v
JOIN comments c
ON v.videoId = c.videoID
GROUP BY v.videoId
ORDER BY commentCount_sum ASC

但是我没有得到正确的commentCount_sum？

Answer 1

您可以在子查询中进行汇总，然后在外部查询中进行窗口计数：

select t.*, sum(commentCount) over(partition by channelId) commentCount_sum
from (
    select v.videoId, v.channelId, count(*) commentCount
    from video v
    inner join comments c on c.videoID = v.videoId and c.videoID_channelID = v.channelId
    group by v.videoId, v.channelId
) t

我还修复了您的加入条件（您在channelId上缺少加入条件）。

Demo on DB Fiddle ：

videoId | channelId | commentCount | commentCount_sum
:------ | :-------- | :----------- | :---------------
a       | 1         | 2            | 5               
b       | 1         | 3            | 5               
c       | 2         | 1            | 2               
d       | 2         | 1            | 2

Answer 2

这可以做到：

SELECT v.videoId,
        v.channelId,
        count(c.textOriginal) commentCount,
        (select count(c.textOriginal) from comments d where d.videoID_channelID = v.channelId group by d.videoID_channelID) as commentCount_sum,
FROM videos v
JOIN comments c
ON v.videoId = c.videoID
GROUP BY v.videoId
ORDER BY commentCount_sum ASC

Answer 3

如果您想不使用window function来执行此操作...我将它们隔开了，您可以看到我们正在做什么。正如GMB所指出的，您缺少在channelID上的加入。

select a.*, b.channel_comment_count
from 

  (select v.videoid, v.channelid, count(c.textoriginal) as video_comment_count
   from cte1 v join cte2 c on v.videoid = c.videoid and v.channelid = c.videoid_channelid 
   group by v.channelid, v.videoid) a

  inner join

  (select channelid, count(c.textoriginal) as channel_comment_count
   from cte1 v join cte2 c on v.videoid = c.videoid and v.channelid = c.videoid_channelid 
   group by v.channelid) b

  on a.channelid=b.channelid

OR

 with cte as
(select v.*, c.textOriginal from cte1 v join cte2 c on v.videoid = c.videoid and v.channelid = c.videoid_channelid)

select a.*, b.channel_comment_count
from 
    (select videoid, channelid, count(textoriginal) as video_comment_count
    from cte group by channelid, videoid) a
    inner join
    (select channelid, count(textoriginal) as channel_comment_count
    from cte group by channelid) b
    on a.channelid=b.channelid

DEMO

获取每个视频的评论和每个视频频道的评论总数

3 个答案: