Question

This is for a custom forum I am working on. i need to select all threads, get the number of posts in each thread and also the last post in each thread. I can get the number of posts, but my query is returning the first post rather than the last.

SELECT thread_id, thread_title, p.*, COUNT(p.post_id) AS Posts
   FROM forums_threads
   JOIN forums_posts AS p ON post_thread_id=thread_id
   WHERE thread_forum_id=84
   GROUP BY thread_id
   ORDER BY thread_date DESC, post_date DESC

Answer 1

As @mixman suggests, you need to link to forum_posts twice: once to get the aggregate amounts (post count and maximum post date), and once to get the actual content of that last post (and I’m assuming that by “last” you mean “most recent”) in the thread:

SELECT ft.thread_id, ft.thread_title, fp.*, pmin.postcount
FROM forums_threads AS ft
JOIN (
      SELECT post_thread_id, MAX(post_date), COUNT(post_id) AS postcount
      FROM forums_posts
      GROUP BY post_thread_id
     ) AS pmin ON ft.thread_id=pmin.post_thread_id
JOIN forums_posts AS fp ON fp.post_thread_id=pmin.post_thread_id AND fp.post_date = pmin.post_date
WHERE ft.thread_forum_id=84
ORDER BY ft.thread_date DESC