在Rails中查询联接关联

Question

广告系列具有:start_date,:end_date属性

发票具有:start_date,:end_date属性

campaign.rb

has_many:invoices

invoice.rb

belongs_to:campaign

我想所有这些cmapaigns其start_date小于当前日期AND其end_date之间campaign.invoices.last.created..current_date

我该如何查询？

Answer 1

尝试这个：

 Compaign.joins(:invoices)
            .where("compaigns.start_date < :today AND compaigns.end_date < :today", today: Date.today)
            .group("compaigns.id")
            .having("compaigns.end_date > MAX(invoices.created_at)")

Answer 2

我从未使用过Rails魔术来对数据库执行或多或少的复杂请求。 它总是会导致大量的开销，N + 1个查询或一些意外的罚款。 这是执行此任务的普通的老式SQL版本：

Campaign.connection.execute <<-SQL
   SELECT campaigns.*, last_invoice_date
   FROM campaigns 
     JOIN (
       SELECT invoices.campaign_id AS campaign_id,
              MAX(invoices.started) AS last_invoice_date
       FROM invoices
       GROUP BY invoices_campaign_id
     ) AS last_invoices
     ON (last_invoices.campaign_id = campaigns.id)
     WHERE campaigns.start_date < NOW()
       AND campaigns.end_date < NOW()
       AND campaigns.end_date >= last_invoices.last_invoice_date
SQL.to_a

出于明显的原因，上面的代码没有经过测试，但是应该可以按原样或稍作修改就可以工作。

Answer 3

campaigns = Campaign.where("DATE(start_date) < ?", Date.today).includes(:invoices)

invoices = campaigns.each do |campaign|
              campaign.invoices.where("Date(campaigns.end_date)" BETWEEN campaign.invoices.last.created_at.to_date AND Date.today)
           end

invoices.map(&:campaign)