Question

首先要做的事情

使用：

rails4
oracle增强适配器rails4分支

我在现有数据库上映射了多对多的关系。我的模型看起来像这样：

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

我这样得到一个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，它应该是 address_id ，而是使用型号名称 entrant_id

这是oracle中增强的错误还是我在表的匹配方面做错了什么？

Answer 1

您的课程的关联未完全定义，但是Event和Entrant都不知道正确的ID，他们应该转到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

它有效，因为event.entrants意味着对数据库执行以下操作（简化）：

加入两个表EventMap和Entrant，以便address_id＆lt; =＆gt; entrant.id （映射1）
在连接表中，使用lottery_event_id = event.id （映射2）找到所有字符串

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]]

Rails 4 oracle增强适配器多对多问题

1 个答案: