5

在我的在线商店中,如果订单处于“授权”状态并且还没有任何关联的发货,则该订单已准备好发货。现在我正在这样做:

class Order < ActiveRecord::Base
    has_many :shipments, :dependent => :destroy

    def self.ready_to_ship
        unshipped_orders = Array.new
        Order.all(:conditions => 'state = "authorized"', :include => :shipments).each do |o|
            unshipped_orders << o if o.shipments.empty?
        end
        unshipped_orders
    end
end

有没有更好的办法?

4

3 回答 3

12

在 Rails 3 中使用 AREL

Order.includes('shipments').where(['orders.state = ?', 'authorized']).where('shipments.id IS NULL')
于 2012-07-17T00:27:16.107 回答
8

您还可以使用正常的 find 语法查询关联:

Order.find(:all, :include => "shipments", :conditions => ["orders.state = ? AND shipments.id IS NULL", "authorized"])
于 2009-04-25T09:16:13.413 回答
3

一种选择是在 Order 上设置 shipping_count,它会根据您附加的货件数量自动更新。那你就

Order.all(:conditions => [:state => "authorized", :shipment_count => 0])

或者,您可以使用一些 SQL 来弄脏您的手:

Order.find_by_sql("SELECT * FROM
  (SELECT orders.*, count(shipments) AS shipment_count FROM orders 
    LEFT JOIN shipments ON orders.id = shipments.order_id 
    WHERE orders.status = 'authorized' GROUP BY orders.id) 
  AS order WHERE shipment_count = 0")

在使用它之前测试它,因为 SQL 不完全是我的包,但我认为它接近正确。我让它适用于我的生产数据库(即 MySQL)上类似的对象排列。

请注意,如果您没有关于 orders.status 的索引,我强烈建议您这样做!

查询的作用:子查询获取所有处于授权状态的订单的所有订单计数。外部查询过滤器仅列出发货计数为零的查询。

可能还有另一种方法可以做到这一点,有点违反直觉:

"SELECT DISTINCT orders.* FROM orders 
  LEFT JOIN shipments ON orders.id = shipments.order_id
  WHERE orders.status = 'authorized' AND shipments.id IS NULL"

获取所有已授权且在发货表中没有条目的订单;)

于 2009-04-25T07:38:27.613 回答