Question

我正在使用Ruby，Sinatra和MySQL。我有四张桌子。

联系人（客户）：

class Contact < ActiveRecord::Base
  attr_accessible :id, :company_id, :name, :address, ...

  has_many :orders, :dependent => :destroy
  has_many :ordered_products
  ...
end

订单：

class Order < ActiveRecord::Base
  attr_accessible :id, :name, :contact_id, ...

  belongs_to :contact  

  has_many :ordered_products, :dependent => :destroy
  has_many :products, :through => :ordered_products
  ...
end

OrderedProducts：

class OrderedProduct < ActiveRecord::Base
  attr_accessible :quantity, :price, :contact_id, :product_id, :order_id ...

  belongs_to :contact
  belongs_to :product
  belongs_to :order
  ...
end

和产品：

class Product < ActiveRecord::Base
  attr_accessible :id, :name, :producer, :region, :size ...

  has_many :ordered_products, :dependent => :destroy
  has_many :orders, :through => :ordered_products
  ...
end

我编写了以下SQL查询，以获取以联系人为中心的统计信息。

SELECT `contacts`.`name`,
  MIN(orderTotals) AS min,
  AVG(orderTotals) AS avg,
  MAX(orderTotals) AS max,
  SUM(`ordered_products`.`price` * `ordered_products`.`quantity`) AS total,
  CAST(COUNT(DISTINCT `orders`.`id`) AS UNSIGNED) AS ordersNumber,
  CAST(SUM(`ordered_products`.`quantity`) AS UNSIGNED) AS productsNumber
FROM `contacts`
INNER JOIN `orders` ON `orders`.`contact_id` = `contacts`.`id`
INNER JOIN `ordered_products` ON `ordered_products`.`order_id` = `orders`.`id`
INNER JOIN `products` ON `products`.`id` = `ordered_products`.`product_id`
INNER JOIN
  ( 
    SELECT contact_id as identifier,
    SUM(`ordered_products`.`price` * `ordered_products`.`quantity`) as orderTotals
    FROM `ordered_products`
    GROUP BY `ordered_products`.`order_id`
  ) `sumTable`
  ON `sumTable`.`identifier` = `contacts`.`id`
WHERE `contacts`.`company_id` = 74
  AND (`orders`.`updated_at` >= '2013-01-01 00:01:59')
  AND (`orders`.`updated_at` <= '2013-12-31 23:59:59')
  AND (`orders`.`order_state_id` = '100')
GROUP BY `contacts`.`id`
ORDER BY `contacts`.`name` ASC
LIMIT 20
OFFSET 0;

我想将其完全翻译为Active Record格式。我能够正确地转换和运行它，但是下面的内部联接让我望而却步，我不得不直接粘贴SQL：

.joins('INNER JOIN (SELECT contact_id as identifier,
SUM(ordered_products.price * ordered_products.quantity) as orderTotals
FROM `ordered_products` GROUP BY ordered_products.order_id) `sumTable`
ON `sumTable`.`identifier` = `contacts`.`id`').

我只报告翻译的SQL查询的一个片段，因为派生表上的连接的翻译对我来说最重要。我发现它不那么优雅和可读，例如：

Contact.joins(orders: [{ordered_products: :product}]). ...

任何帮助将不胜感激！

谢谢，卢卡

Answer 1

由于其他代码不存在，无法完全告诉您要执行的操作，但如果您使用的是Postgres，则可能需要查看pg_search gem，因为它可能会为您节省一些SQL工作看起来这可能会成为更新/维护的痛苦。

在派生表上使用复杂连接的Active Record查询？

1 个答案: