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父级的简单Rails嵌套关联where子句有问题

rails-activerecord ruby-on-rails

Augusto Samamé Barrientos · 技术社区 · 6 年前

class Business < ApplicationRecord
  has_many :shopping_trips
end

class ShoppingTrip < ApplicationRecord
  belongs_to :business
  has_many :purchases
end

class Purchase < ApplicationRecord
  belongs_to :shopping_trip
end

所以一个企业可以有很多次购物旅行,而且每一次购物旅行都可以有很多次购物。

我试图在Purchase表上运行一个简单的查询,以查找属于特定业务的采购。所以我写这个:

purchases = Purchase.joins(:shopping_trip => :business ).where(:shopping_trip => {:business_id => 1})

不幸的是它不起作用。我得到以下错误:

ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "shopping_trip"
LINE 1: ...sses"."id" = "shopping_trips"."business_id" WHERE "shopping_...
                                                             ^
: SELECT "purchases".* FROM "purchases" INNER JOIN "shopping_trips" ON "shopping_trips"."id" = "purchases"."shopping_trip_id" INNER JOIN "businesses" ON "businesses"."id" = "shopping_trips"."business_id" WHERE "shopping_trip"."business_id" = $1

join看起来是正确的,但where子句似乎失败了。

3 回复 | 直到 6 年前

Pavan Cesar 6 年前

ActiveRecord::StatementInvalid:PG::UndefinedTable:错误:缺少

表名 where . 所以呢 shopping_trip 应该是 shopping_trips

purchases = Purchase.joins(:shopping_trip => :business ).where(:shopping_trips => {:business_id => 1})

max 6 年前

更好的解决方案是设置间接关联,这样您就可以通过联接模型进行查询,而无需手动联接:

class Business < ApplicationRecord
  has_many :shopping_trips
  has_many :purchases, through: :shopping_trips
end

class ShoppingTrip < ApplicationRecord
  belongs_to :business
  has_many :purchases
end

class Purchase < ApplicationRecord
  belongs_to :shopping_trip
  has_one :business, through: :shopping_trip
end

您现在可以从任意一侧进行查询:

@business = Business.eager_load(:purchases).find(1)
@purchases = @business.purchases

# or
@purchases = Purchase.eager_load(:buisness).where(businesses: { id: 1 })

-1

Arun P 6 年前

检查这个。。。

所有购买=购买.all

结束

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