Rails 3 在一个查询中包含多个表

Question

我正在开发一个用于锦标赛的 Rails 应用程序。我在这个查询上使用了三个模型：

class Player < ActiveRecord::Base
  validates :name, :uniqueness => true
  has_and_belongs_to_many :tournaments

class Tournament < ActiveRecord::Base
  belongs_to :tournament_type
  has_and_belongs_to_many :players
  has_many :player_matches, :dependent => :destroy

class PlayerMatch < ActiveRecord::Base
  belongs_to :player_one, :class_name => "Player", :foreign_key => "player_one"
  belongs_to :player_two, :class_name => "Player", :foreign_key => "player_two"

在锦标赛控制器的显示操作中，我调用以下查询：

Tournament.where(:id => params[:id]).includes(:player_matches, :players).first()

虽然锦标赛和玩家匹配是在单个连接中完成的，但玩家是单独查询的，因为我的代码依赖于他们：

Player Load (0.4ms)  SELECT `players`.*, t0.tournament_id as the_parent_record_id FROM `players` INNER JOIN `players_tournaments` t0 ON `players`.id = t0.player_id WHERE (t0.tournament_id = 14)
Player Load (0.2ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 5 LIMIT 1
Player Load (0.2ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 9 LIMIT 1
Player Load (0.2ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 1 LIMIT 1
Player Load (0.1ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 8 LIMIT 1
Player Load (0.1ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 3 LIMIT 1
Player Load (0.1ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 2 LIMIT 1
Player Load (0.1ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 7 LIMIT 1
Player Load (0.1ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 6 LIMIT 1
Player Load (0.1ms)  SELECT `players`.* FROM `players` WHERE `players`.`id` = 4 LIMIT 1

我怎样才能改变这一点，以便将其全部提取到一个查询中？

Answer 1

Tournament.where(:id => params[:id]).includes([{:player_matches => :player_one}, :players]).first()

那应该可以解决问题。实际上，数组表示法和哈希表示法的组合一开始排序有点混乱，但是使用控制台，您会发现哪种语法不会崩溃:)