Question

我需要的-是从4个表中获取数据。我需要有用户国家（地区），main_services名称，只有exportable: true以及连接到main_service的每个最后一个Reservation_line中的数量。

这些是我模型的连接和表字段：

Reservatoin.rb：

# == Schema Information
#
# Table name: reservations
#
#  id                  :integer          not null, primary key
#  from_date           :date
#  to_date             :date
#  ...
#

class Reservation < ApplicationRecord
  belongs_to :user
  has_many :reservation_lines, dependent: :destroy
end

User.rb：

# == Schema Information
#
# Table name: users
#
#  id                     :integer          not null, primary key
#  ...
#  country                :string(255)

class User < ApplicationRecord
  has_many :reservations, dependent: :destroy
end

ReservationLine.rb：

# == Schema Information
#
# Table name: reservation_lines
#
#  id                 :integer          not null, primary key
#  reservation_id     :integer
#  quantity           :integer
#  serviceable_type   :string(255)
#  serviceable_id     :integer
#

class ReservationLine < ApplicationRecord
  belongs_to :reservation
  belongs_to :serviceable, polymorphic: true, optional: true
end

MainService.rb：

# == Schema Information
#
# Table name: main_services
#
#  id                  :integer          not null, primary key
#  name                :string(255)
#  main_service        :boolean          default(FALSE)
#  input_type          :string(255)
#  exportable          :boolean          default(FALSE)
#

class MainService < ApplicationRecord
  has_many :reservation_lines, as: :serviceable
end

因此，我决定编写一个作用域。看起来像这样：

预订模式：

scope :nationalities_with_date_test, -> (from, to) { joins(:user)
                                                      .joins(:reservation_lines)
                                                      .joins('INNER JOIN main_services ON main_services.id = reservation_lines.serviceable_id')
                                                      .where('reservation_lines.serviceable_type =?', 'MainService')
                                                      .where('main_services.exportable =?', true)
                                                      .select('users.country, main_services.name, SUM(reservation_lines.quantity) as quantity')
                                                      .where('reservations.from_date <= ? AND reservations.to_date >= ? AND (reservations.aasm_state = ? OR reservations.aasm_state = ? OR reservations.aasm_state = ?)',
                                                             to,
                                                             from,
                                                             'in_place', 'closed', 'finished')
                                                      .group('users.country')
                                                     }

如您所见，我将reservation_lines表中的所有数量都拿走了，但是我只需要为每个main_service都拿走最后一个，而我不知道该怎么办甚至根本没有可能。任何帮助，将不胜感激。谢谢。

从Rails的4个联接表中获取数据

0 个答案: