使用doctrine2在symfony2中加入子查询

Question

我试图在我的symfony2应用程序中执行以下SQL。

SQL的摘要是

Select the latest currency conversion rate for each branch.
The currencies should be active.
The branches should be verified.

原始SQL是

SELECT b.id, r1.* FROM rate as r1 JOIN 
 ( SELECT branch, from_currency, to_currency, max ( time ) as latest_time FROM `rate` group by branch, from_currency, to_currency ) as r2 
 ON r1.branch = r2.branch 
    and r1.from_currency = r2.from_currency 
    and r1.to_currency = r2.to_currency 
    and r1.time = r2.latest_time
 join branch b 
    on b.id = r1.branch and b.verified_by is not null
 join currency c1
    on r1.from_currency = c1.id 
 join currency c2
    on r1.to_currency = c2.id
 where c1.active = 1 and c2.active = 1

首先，我尝试使用querybuilder在这种情况下似乎不受支持。 现在我意识到我需要使用NativeQuery。 但是我对填充ResultSetMapping感到困惑。 我一直在关注http://doctrine-orm.readthedocs.org/en/latest/reference/native-sql.html，但无法真正表达清楚。

问题是：

• 谁能帮我在这里填充结果集吗？
• 还是获取结果集的更好方法？

PS让我知道是否也应该添加架构。 为了简洁起见，我跳过了它。