Question

我有两张桌子：

带有字段的cc_videos：id，challenge_id，upload_date，owner_id
cc_video_votes，包含字段ID，video_id，vote_date

Field＆＃34; id＆＃34;在＆＃34; cc_videos＆＃34;对应一个字段＆＃34; video_id＆＃34; in＆＃34; cc_video_votes＆＃34;我有这样的陈述：

SELECT cc_videos.*, COUNT(video_id) AS votes_count
FROM cc_videos LEFT JOIN cc_video_votes
ON cc_videos.id = cc_video_votes.video_id
GROUP BY cc_videos.id
ORDER BY votes_count desc

现在这样可以正常工作 - 列出所有视频按照具有最高投票率的视频排序。现在我想条件只列出来自＆＃34; cc_videos＆＃34;的视频。 WHERE challenge_id匹配变量＆＃34; $ challenge_id＆＃34;，但是当我放置这样的条件时它返回0结果：

SELECT cc_videos.*, COUNT(video_id) AS votes_count
FROM cc_videos WHERE challenge_id = "$challenge_id"
LEFT JOIN cc_video_votes
ON cc_videos.id = cc_video_votes.video_id
GROUP BY cc_videos.id
ORDER BY votes_count desc

我是否正确使用WHERE子句？

Answer 1

不，你不是。

SELECT cc_videos.*, COUNT(video_id) AS votes_count
FROM cc_videos 
LEFT JOIN cc_video_votes
ON cc_videos.id = cc_video_votes.video_id
WHERE cc_videos.challenge_id = "$challenge_id"
GROUP BY cc_videos.id
ORDER BY votes_count desc

WHERE语法应保留在子句check documentation here

中

Answer 2

将您的查询更改为：

SELECT cc_videos.*,
       Count(video_id) AS votes_count
FROM   cc_videos
       LEFT JOIN cc_video_votes
              ON cc_videos.id = cc_video_votes.video_id
WHERE  cc_videos.challenge_id = "$challenge_id"
GROUP  BY cc_videos.id
ORDER  BY votes_count DESC

MySQL将连接计数与条件保持一致

2 个答案: