Intelligent MySQL GROUP BY for Activity Streams

Question

I\'m building an activity stream for our site, and have made some decent headway with something that works pretty well.

It\'s powered by two tables:

Answer 1

My impression is you need to group by user, as you do, but also, after that grouping, by action.

It looks to me like you need a subquery like this:

SELECT *, -- or whatever columns
   SUM(actions_in_group) AS total_rows_in_group,
   GROUP_CONCAT(in_collection) AS complete_collection
   FROM
     ( SELECT stream.*, -- or whatever columns
          COUNT(stream.id) AS actions_in_user_group,
          GROUP_CONCAT(stream.id) AS actions_in_user_collection
       FROM stream
       INNER JOIN follows
       ON stream.user_id = follows.following_user
       WHERE follows.user_id = '1'
         AND stream.hidden = '0'
       GROUP BY stream.user_id,
            date(stream.stream_date)
     )
   GROUP BY object_id,
            date(stream.stream_date)
   ORDER BY stream.stream_date DESC;

Your initial query (now the inner one) groups by user, but then the user groups are regrouped by identical actions - that is, identical products bought or sales from one seller would be put together.