Question

I am building a forum using Oracle as my rdbms and I am having problems with 1 query that fetches all the forum posts and displays some data. The issue I am having is getting the last discussion poster. With my query I only managed to get the last poster’s id , but I want to get his username from the users table. This is what I have:

I have the following schema:

discussions
    id 
    course_id
    user_id
    title
    stub
    created_at

threads
    id
    discussion_id
    user_id
    created_at
    updated_at
    message

 discussion_views
     discussion_id
     user_id
     time

  users
     id
     username`

And I make this query:

select * from
(select discussions.created_at, 
        discussions.title, 
        users.username as discussion_created_by, 
        count(distinct threads.id) over (partition by discussions.created_at, 
                                                      discussions.title, 
                                                      users.username) AS replies, 
        count(distinct discussion_views.discussion_id) 
             over (partition by discussions.created_at, 
                                discussions.title, 
                                users.username) AS "views",
        threads.user_id AS latest_post_by,
        threads.updated_at AS latest_post_at,
        row_number() over (partition by discussions.created_at, 
                                        discussions.title, 
                                        users.username
                           order by threads.id desc) AS rn
 from discussions
 left join threads on discussions.id=threads.discussion_id
 left join discussion_views on discussions.id=discussion_views.discussion_id
 join users on users.id=discussions.user_id) sq
where rn=1
order by created_at desc

I am getting latest_post_by as id , I want to display the username

Answer 1

In response to your comment, add another join to the users table.

join users latest_poster ON (latest_poster.id=threads.user_id)

Then replace:

threads.user_id AS latest_post_by

with:

latest_poster.username AS latest_post_by

This should then give you the username of the user identified by threads.user_id.

Hope it helps…