MySQL - how to show the latest topic per thread

Question

I am trying to create SQL for retrieveing a list of latests posts for the forum thread. I have the following code:

SELECT
 item_discuss_thread_id
 , item_dis         


        

Answer 1

Try this.

SELECT
  *
FROM
  (SELECT item_discuss_thread_id, item_discuss_post_title, COUNT(item_discuss_thread_id) AS nb_posts
   FROM item_discuss_posts
   ORDER BY __datecolumn__)
  AS ordered_by_date
GROUP BY
  ordered_by_date.item_discuss_thread_id

Replace __datecolumn__ with the column that stores posting time.

Answer 2

Ok, I came with solution myself. I used a dependent subquery to solve. This is what I have in the result:

        SELECT
             item_discuss_threads.item_discuss_thread_id
             , item_discuss_threads.item_discuss_thread_datetime
             , item_discuss_threads.item_discuss_thread_title
             , latest_posts.item_discuss_post_title
             , latest_posts.item_discuss_post_datetime
             , COUNT(item_discuss_posts.item_discuss_post_id) AS nb_posts
        FROM
             item_discuss_threads
        INNER JOIN item_discuss_posts
             ON item_discuss_threads.item_discuss_thread_id=item_discuss_posts.item_discuss_thread_id
        INNER JOIN item_discuss_posts AS latest_posts
             ON latest_posts.item_discuss_thread_id=item_discuss_threads.item_discuss_thread_id
        WHERE
             (
                  SELECT
                        item_discuss_post_id
                  FROM
                        item_discuss_posts AS p
                  WHERE
                        p.item_discuss_thread_id=item_discuss_posts.item_discuss_thread_id
                  ORDER BY
                        item_discuss_post_datetime DESC
                  LIMIT
                       1
             )=latest_posts.item_discuss_post_id
        GROUP BY
             item_discuss_threads.item_discuss_thread_id
        ORDER BY
            latest_posts.item_discuss_post_datetime DESC