Rails - 如何将 find_by_sql （数组）的输出转换为 ActiveRecord 关系？答案

【问题标题】：Rails - how to convert output of find_by_sql (array) to an ActiveRecord relation?Rails - 如何将 find_by_sql （数组）的输出转换为 ActiveRecord 关系？
【发布时间】：2021-01-21 14:37:36
【问题描述】：

我需要运行一个复杂的 SQL 查询，因为我不知道如何使用 ActiveRecod 构造查询，所以我不得不通过 find_by_sql 使用原始 SQL 查询：

scope :get_cars, -> do
    find_by_sql('select * from
                  (SELECT cars.*,
                     manufacturer.company_name AS manufacturer_company_name,
                     services.a_num AS service_a_num,
                     (SELECT car_documents.file_url FROM car_documents
                       WHERE car_documents.car_id = cars.id AND car_documents.doc_type = 1 LIMIT 1) AS doc1_file_url,
                     (SELECT car_documents.file_s3_url FROM car_documents
                       WHERE car_documents.cart_id = cars.id AND car_documents.doc_type = 3 LIMIT 1) AS file_inv,
                     (SELECT car_data.demand_lvl FROM car_data
                       WHERE car_data.car_id = cars.id) AS demand_lvl,
                     (SELECT car_logs.invoice FROM car_logs
                       WHERE car_logs.car_id = cars.id AND car_logs.invoice = 1 LIMIT 1) AS invoice_sent
                   FROM "cars"
                   INNER JOIN "services" ON "services"."id" = "cars"."service_id"
                   LEFT JOIN manufacturers ON manufacturers.id = cars.manufacturer_id
                   WHERE (cars.status_id != 6
                          AND cars.delivery_date < NOW() - INTERVAL \'15 days\'
                    ) ORDER BY cars.pickup_date ASC) t
                 Where doc1_file_url IS NULL OR file_inv IS NULL OR invoice_sent IS NULL')
  end

输出是一个数组。如何将此数组转换为 ActiveRecord 对象？或者可能，有什么解决方法吗？

【问题讨论】：

将其转换为 AR 查询将变得容易得多，并且不那么 hacky，然后反过来。为了帮助您完成我们需要您的模型和架构示例。

标签： sql ruby-on-rails activerecord

【解决方案1】：

我认为，您可以使用 Active Record 接口中的from() 方法。您可以借助from() 方法将子查询用作SQL 选择语句的表。检查下面的例子。这样就得到了活动记录对象。

subquery = Setting.limit(10)
Setting.from("(#{subquery.to_sql}) settings")

在你的情况下，

subquery = "(SELECT cars.*,
                     manufacturer.company_name AS manufacturer_company_name,
                     services.a_num AS service_a_num,
                     (SELECT car_documents.file_url FROM car_documents
                       WHERE car_documents.car_id = cars.id AND car_documents.doc_type = 1 LIMIT 1) AS doc1_file_url,
                     (SELECT car_documents.file_s3_url FROM car_documents
                       WHERE car_documents.cart_id = cars.id AND car_documents.doc_type = 3 LIMIT 1) AS file_inv,
                     (SELECT car_data.demand_lvl FROM car_data
                       WHERE car_data.car_id = cars.id) AS demand_lvl,
                     (SELECT car_logs.invoice FROM car_logs
                       WHERE car_logs.car_id = cars.id AND car_logs.invoice = 1 LIMIT 1) AS invoice_sent
                   FROM "cars"
                   INNER JOIN "services" ON "services"."id" = "cars"."service_id"
                   LEFT JOIN manufacturers ON manufacturers.id = cars.manufacturer_id
                   WHERE (cars.status_id != 6
                          AND cars.delivery_date < NOW() - INTERVAL \'15 days\'
                    ) ORDER BY cars.pickup_date ASC)"

【讨论】：