3个表的mysql查询

此查询不选择，无评论或无表决数据，我如何解决？3个表的mysql查询

SELECT 
    blog_posts.*, 
    COUNT(DISTINCT(blog_comments.CommentID)) AS CountComments, 
    COUNT(DISTINCT(blog_votes.VoteID)) AS CountVotes, 
    AVG(DISTINCT(blog_votes.Vote)) AS AvgVote 
    FROM blog_posts 
    INNER JOIN blog_comments ON blog_comments.CommentBlogID=blog_posts.BlogID 
    INNER JOIN blog_votes ON blog_votes.VoteBlogID=blog_posts.BlogID 
    ORDER BY blog_posts.BlogID 
    LIMIT 0,10

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2015-09-22 Eren Özkul

'GROUP BY blog_post.col1，blog_posts.col_2，...' – lad2025

所以你想计数评论，投票和平均投票数据？ –

@MichaelAntonio它的真实 –

这个怎么样，我使用子查询，使之简单：

SELECT b.*, 
    COUNT(select CommentID from blog_comments where CommentBlogID = b.BlogID group by CommentID) as CountComments, 
    COUNT(select VoteID from blog_comments where VoteBlogID = b.BlogID group by VoteID) as CountVotes, 
    AVG(select Vote from blog_comments where VoteBlogID = b.BlogID group by Vote) as AvgVote, 
FROM blog_posts as b 
ORDER BY b.BlogID 
LIMIT 0,10

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2015-09-22 00:58:31

＃1064 - 你的SQL语法有错误;请查看与您的MySQL服务器版本相对应的手册，以便在'SELECT blog_comments.CommentID FROM blog_comments WHERE blog_com'的第3行 –

我固定

SELECT 
blog_posts.*, 
COUNT(VoteID) as CountVotes, 
AVG(VoteID) As AvgVotes, 
COUNT(CommentID) AS CountComments 
FROM blog_posts 
LEFT JOIN blog_votes ON blog_posts.BlogID = blog_votes.VoteBlogID 
LEFT JOIN blog_comments ON blog_posts.BlogID = blog_comments.CommentBlogID 
GROUP BY blog_posts.BlogID 
ORDER BY BlogID DESC 
LIMIT 0,10

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2015-09-22 02:16:09

3个表的mysql查询

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