Active Record Insert Into

Question

I am trying to allow my Rails App some advanced functionality in way of creating relationships. I am running MySQL as the back-end. The query below runs just fine in PHPMyAdmin, but upon attempted execution in rails, it does nothing, no errors and no database writes....

I use active record to create the relationships between Campaign and Location, and then the query below should work to build afterward in campaign_metros table:

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

I know from MySQL DELETE FROM with subquery as condition, in answer number two by CodeReaper, that MySQL requires another level of aliases when dealing with subqueries, but running my query in Rails does nothing at all.

How can I get this to work?

Dulcedulcea

It turns out that all I had to do was not save as a variable, ie @sql_insert, but simply sql_insert, it all works fine now – Dulcedulcea