1

第一件事

使用：

  • 导轨4
  • oracle 增强型适配器 rails4 分支

我在现有数据库上映射了多对多关系。我的模型如下所示：

class EventMap < ActiveRecord::Base
  self.table_name="TAKE_PART"
  self.primary_key="id"
  belongs_to :event, foreign_key: "lottery_event_id"  
  belongs_to :entrant, foreign_key: "address_id"  
end

class Event < ActiveRecord::Base
  self.table_name="THE_EVENT"
  self.primary_key="id"
  has_many :event_maps
  has_many :entrants, :through => :event_maps
end

class Entrant < ActiveRecord::Base
  self.table_name="ADDRESSES"
  self.primary_key="id"
  self.set_date_columns :date_of_birth
  has_many :event_maps
  has_many :events, :through => :event_maps
end

当我尝试获取事件的所有地址时：

  def show
    @entrants = Event.find(params[:id]).entrants
  end

我收到这样的 Oracle 错误：

OCIError: ORA-00904: "TAKE_PART"."ENTRANT_ID": SELECT "THE_EVENT".* FROM "THE_EVENT" INNER JOIN "TAKE_PART" ON "THE_EVENT"."ID" = "TAKE_PART"."LOTTERY_EVENT_ID" WHERE "TAKE_PART"."ENTRANT_ID" = :a1

这里的问题似乎是 TAKE_PART 的外键没有正确使用，应该是address_id，而是使用模型名称entrant_id

这是oracle增强中的错误还是我在匹配表时做错了什么？

4

1 回答 1

1

你的类的关联没有完全定义，bcEvent既不Entrant知道正确的id，它们应该传递给EventMap. 正确的方法如下： 

class EventMap < ActiveRecord::Base
  ...
  belongs_to :event, :foreign_key => "lottery_event_id"  
  belongs_to :entrant, :foreign_key => "address_id"
end

class Event < ActiveRecord::Base
  ...
  has_many :event_maps, :foreign_key => "lottery_event_id"
  has_many :entrants, :through => :event_maps
end

class Entrant < ActiveRecord::Base
  ...
  has_many :event_maps, :foreign_key  => "address_id"
  has_many :events, :through => :event_maps
end

它之所以有效，是因为event.entrants暗示了对数据库的以下操作（简化）：

连接两个表EventMap和Entrant，以便 address_id <=> entrant.id （映射 1）
在连接表中找到所有带有 lottery_event_id = event.id 的字符串（映射 2）

映射 1：

has_many :entrants, :through => :event_maps         #Join two tables
belongs_to :entrant, :foreign_key => "address_id"   #matching address_id with entrants.id
#belongs_to+foreign_key tells to EventMap which key to use for referring to Event object

映射2：

has_many :event_maps, :foreign_key => "lottery_event_id" #associate event.id with lottery_event_id
#has_many+foreign_key tells to Event which key EventMap uses for referring to Event object

或者以更正式的方式： 

SELECT "entrants".* FROM "entrants" INNER JOIN "event_maps" ON "entrants"."id" =
"event_maps"."address_id" WHERE "event_maps"."lottery_event_id" = ?  [["lottery_event_id", 1]]
于 2013-10-24T13:28:50.850 回答