多对多关系上的单个SQL查询

你可以使用 GROUP_CONCAT 功能

select p.*, group_concat(DISTINCT c.title ORDER BY c.title DESC SEPARATOR ', ')
from Posts p
inner join PostCategories pc on p.ID = pc.ID_Post
inner join Categories c on pc.ID_Category = c.ID
group by p.id, p.title, p.content

简单连接工作良好。

SELECT posts.id, posts.title, categories.id, categories.title
FROM posts
JOIN posts_categories ON posts.id = posts_categories.post_id
JOIN categories ON posts_categories.category_id = categories.id

select p.*, c.*
from Posts p
inner join PostCategories pc on p.ID = pc.ID_Post
inner join Categories c on pc.ID_Category = c.ID

如果您的意思是每个日志只有一个记录,那么我需要知道您使用的是什么数据库平台。

当然。如果我正确理解你的问题,它应该像

SELECT Posts.title, Categories.title 
FROM Posts, Categories, PostCategories 
WHERE PostCategories.ID_Post = Posts.ID AND PostCategories.ID_Category = Categories.ID 
ORDER BY Posts.title, Categories.title;

每个帖子获得一行会更复杂一些,这将取决于您使用的RDBMS。