SQL查询INNER JOIN三个用表

Question

有这三个表：

1. 帖子
2. posts_replies
3. 喜欢

该查询返回我的帖子及其回复数无一不精。 SELECT posts.title，posts.num，posts.status，posts.category，posts.content，posts.member_num，COUNT（posts_replies.blyrb_num）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 

记录该查询返回的是：47

这是一个更新的查询，我想拉动每个帖子的回复的喜欢次数。

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 

此查询返回的是喜欢的数量好，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

我想包括每个回复的Like Count，即使它有0个喜欢。

任何帮助？

谢谢

Answer 1

使用的LEFT JOIN代替INNER JOIN可能会帮助你在这里

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 

的LEFT JOIN想法是匹配行，即使没有人会在右侧匹配。 INNER JOIN只适用于双方都有行的情况。 :)