如何在MySQL中使用两个条件进行内部联接

Question

I have two tables in mysql database they are like following:

USERS : id, username
POSTS : id, post, poster_id, posted_id

Now I want to get the last 10 posts with the username of the poster_id(the man who wrote the post) and the username of the posted_id(the owner of the wall where the post has been written)

I use this query :

SELECT posts.*,users.username as poster_username FROM posts
INNER JOIN users on posts.poster_id = users.id 
ORDER BY timestamp DESC 
LIMIT 0,10

but as you can see I just get one username for the poster_id is there a way to get the username of the posted_id within the same inner join statement??

Answer 1

You should join user for twice:

SELECT posts.*,
       u1.username as poster_username,
       u2.username as posted_username
FROM posts
INNER JOIN users u1 on posts.poster_id = u1.id 
INNER JOIN users u2 on posts.posted_id = u2.id 
ORDER BY timestamp DESC 
LIMIT 0,10

The only requirement is to assign an alias to each table