Sql 在rails 3.1中将子查询用作表

我正在尝试从另一个查询中选择一些数据。 SQL将如下所示：

SELECT user_id, rank FROM 
(SELECT user_id, MAX(created_at) as latest_solution, COUNT(*) AS solved,
rank() OVER (ORDER by COUNT(*) desc) AS rank FROM submissions group by user_id) 
as leaderboard WHERE leaderboard.user_id = xx

但我很难把它翻译成activerecord语言

我认为我对以下子查询没有问题：

Submission.select('user_id, MAX(created_at) as latest_solution, COUNT(*) as solved, rank() OVER (ORDER BY count(*) desc) as rank').group('user_id')

但我不知道如何将其用作“表格”。

对于任何非琐碎的事情，我都会直截了当地说：

Submission.find_by_sql(%q{
    select user_id,
           rank
    from (
        select user_id,
               max(created_at) as latest_solution,
               count(*) AS solved,
               rank() over (order by count(*) desc) as rank
        from submissions
        group by user_id
    ) as leaderboard
    where leaderboard.user_id = :user_id
}, :user_id => 'xx')

在

Submission

上用class方法包装它，您应该会没事的