Question

我在将以下SQL查询转换为ActiveRecord查询时遇到了麻烦。这将是原始SQL中的查询：

SELECT customers.name, customers.email, customers.address, (sales.quantity * sales.price AS total_spent)
FROM customers JOIN sales ON customers.id = sales.customer_id
GROUP BY customers.id
ORDER BY total_spent DESC

我这样做是为了开始为订购顶级客户而开始工作，但它不起作用：

Customer.joins(:buys).group("customers.id").select("id", "name", "price"*"stock" as "total_buys")

任何帮助都会非常感激。

感谢。

Answer 1

首先设置你的模型关联并添加一些方便的方法

class Customer < ActiveRecord::Base
  has_many :sales

  # if you add a subtotal field that is autocalculated you could also do this
  def total_spent
    self.sales.all.map(|sale| sale.total ).sum 
  end
end

class Sale < ActiveRecord::Base
  belongs_to :customer

  def total
    self.price * self.amount
  end
end

然后在您的应用或控制台中输入：

Customer.first.sales.map(&:total).sum

或所有客户：

Customer.all.each{ |c| puts c.sales.map(&:total).sum }

将SQL转换为ActiveRecord查询

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