Question

I have the following 3 tables:

users:
id, username

folders:
id,fkuser(connects to user.id)

folder_comments:
id,fkuser(connects to user.id), fkfolder(connects to folder.id)

I want to get the commenter username(folder_comments.fkuser->user.id<->user.username) AND and the username of the folder owner (folder_comments.fkfolder->folder.id<->folder.fkuser->user.id<->user.username);

The query I have thoght of is partial:

SELECT `folder_comments`.*, `folder`.`fkuser` as folderuserid, `user`.`firstname` as username
FROM `folder_comments` 
                left join `folder` on `folder_comments`.`fkfolder` = `folder`.`id`
                left join `user` on `folder_comments`.`userid` = `user`.`id`

How can I get the folder’s owner username?

edit :

I tried:

    SELECT `folder_comments`.*, `folder`.`fkuser` as folderuserid, `user`.`firstname` as username, , `user`.`firstname` as folderowner
        FROM `folder_comments` 
                        left join `folder` on `folder_comments`.`fkfolder` = `folder`.`id`
                        left join `user` on `folder_comments`.`userid` = `user`.`id`
left join `user` on `folder`.`fkuser` = `user`.`id`

but I get an error Not unique table/alias: 'user'

Answer 1

use user in join multiple times, something like this:

select folder.*, userfolder.username, comment.*, usercomment.username
  from folders folder inner join
  user userfolder on folder.fkuser = userfolder.id inner join
  comments comment on comment.fkfolder = folder.id inner join
  user usercomment on comment.fkuser = usercomment.id

when using the same table multiple times in a join it’s important you use different alias