group by

What I'm trying to do here, is I want to output the count of the `id` and `user_id` columns from `items`, by users which have the rank `1`. Let's say there's 8 rows in `items` which have a `base_item` of 400, and these 8 rows, where 2 rows of them has a `user_id` of 4 and the existing left has a...