活动记录插入

Question

我正在尝试允许我的Rails应用程序创建关系的一些高级功能。我正在运行MySQL作为后端。下面的查询在PHPMyAdmin中运行得很好，但是在rails中尝试执行时，它什么都不做，没有错误，也没有数据库写入....

我使用活动记录来创建Campaign和Location之间的关系，然后下面的查询应该可以在campaign_metros表中构建：

class CampaignLocation < ActiveRecord::Base
    belongs_to :campaign
    belongs_to :location

    after_touch :create_campaign_metro


    private
        def create_campaign_metro
            @sql_insert="INSERT INTO `campaign_metros` (`campaign_id`,`metro_id`, `created_at`,`updated_at`)
                    SELECT f.`campaign_id`, f.`city_id`, NOW(), NOW()
                    FROM (SELECT d.`campaign_id`, d.`city_id`
                        FROM (SELECT c.`campaign_id`, c.`city_id` 
                              FROM  (SELECT distinct a.`campaign_id`, b.`city_id`
                                        FROM `campaign_locations` a
                                        INNER JOIN `locations` b 
                                        ON a.`location_id` = b.`id`) c) d
                        LEFT JOIN `campaign_metros` e
                            ON e.`campaign_id` = d.`campaign_id` and
                               e.`metro_id`    = d.`city_id`
                        WHERE e.`metro_id` is null and e.`campaign_id` is null) f;"

            ActiveRecord::Base.connection.execute(@sql_insert)
        end
end

我从MySQL DELETE FROM with subquery as condition知道，在CodeReaper的第二个答案中，MySQL在处理子查询时需要另一级别的别名，但在Rails中运行我的查询什么都不做。

我怎样才能让它发挥作用？