具有三个表的SQL查询INNER JOIN

Question

有以下三个表：

1. 帖子
2. posts_replies
3. 喜欢

该查询返回了我的帖子，并且它们的回复都很好。 SELECT posts.title，posts.num，posts.status，posts.category，posts.content，posts.member_num，COUNT（posts_replies.blyrb_num）个AS计数

FROM posts_replies
INNER JOIN posts ON ( posts_replies.blyrb_num = posts.num )
WHERE posts.status =1
AND posts.access = 'Public'
GROUP BY posts.num
ORDER BY count DESC
LIMIT 50 

该查询返回的记录是：47

这是一个有点更新的查询，我想提取每个帖子回复的“赞”计数。

SELECT posts.title, posts.num, posts.status, posts.category, posts.content, posts.member_num, 
COUNT( posts_replies.blyrb_num ) AS count,
COUNT( likes.comment_num  ) AS likes_count
FROM posts_replies
INNER JOIN posts ON ( posts_replies.blyrb_num = posts.num )
INNER JOIN likes ON ( likes.comment_num = posts_replies.num )
WHERE posts.status =1
AND posts.access = 'Public'
GROUP BY posts.num
ORDER BY count DESC
LIMIT 50 

该查询返回的“喜欢计数”很好，但不包括那些没有“喜欢”的记录。 因此此查询返回的记录是：40

我希望包括每个回复的“喜欢计数”，即使它有0个喜欢。

有什么帮助吗？

谢谢

Answer 1

使用LEFT JOIN代替INNER JOIN可能对您有帮助

SELECT posts.title, posts.num, posts.status, posts.category,
posts.content,posts.member_num, 
COUNT( posts_replies.blyrb_num ) AS count,
COUNT( likes.comment_num  ) AS likes_count
FROM posts_replies
INNER JOIN posts ON ( posts_replies.blyrb_num = posts.num )
LEFT JOIN likes ON ( likes.comment_num = posts_replies.num )
WHERE posts.status = 1
AND posts.access = 'Public'
GROUP BY posts.num
ORDER BY count DESC
LIMIT 50 

LEFT JOIN的想法是匹配行，即使右侧没有要匹配的行也是如此。 INNER JOIN仅在双方都有行时才起作用。 :)