ruby-on-rails - How would I do this query with Arel?

Question

I have a User model and an Item model. I want to rank users according to the value of the items they have. I want to do the equivalent of this query:

SELECT rank() OVER (ORDER BY grand_total DESC), u.*, grand_total
FROM users AS u
JOIN
(SELECT user_id, SUM(amount) AS grand_total FROM items WHERE EXTRACT(YEAR FROM sold_at)='2012' GROUP BY user_id) AS i
ON u.id = i.user_id;

Specifically, I don't know how to join on my select.

Answer 1

鉴于您描述的问题，我将这样编写查询：

select users.*, sum(items.amount) as rank
  from users
  join items on items.user_id = users.id
  group by users.id
  order by rank desc;

这将转化为 AREL：

User.select('users.*, sum(items.amount) as rank').joins('join items on items.user_id = users.id').group('users.id').order('rank desc')

这有一个方便的副作用，您可以调用.rank生成的 User 对象并从查询中获取排名列的值，以防您需要显示它。

你的情况有什么我在这里没有掌握的吗，或者这会起作用吗？