使用子查询作为rails 3.1上的表

Question

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

但是我在尝试将其翻译成activerecord语言时遇到了麻烦

我觉得我对子查询没问题

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

但我不知道如何使用它作为"表"

Answer 1

我直接去find_by_sql寻找任何不平凡的事情:

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')

在类方法中包装,Submission你应该没问题.