Mysql 如何对rails中的4个表使用联接查询

我有下面的表4模型

class ItemCode < ActiveRecord::Base
  belongs_to :item_point
end

class ItemPoint < ActiveRecord::Base
  belongs_to :item
  has_many :item_codes
end

class Item < ActiveRecord::Base
  belongs_to :prodcut_category
  has_many :item_points
end

class ProductCategory < ActiveRecord::Base  
  has_many :items
end

现在我必须以Acitve记录格式编写相同的查询

ItemCode.joins(:item_point).joins(:item).joins(:product_catagory).where("product_catagories.id = 1")

获取以下错误

ActiveRecord::ConfigurationError: Association named 'item_points' was not found; perhaps you misspelled it?

那么如何以活动记录格式编写给定的查询呢

编辑

产品类别

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| client_id            | int(11)      | YES  |     | NULL    |                |
| category_name        | varchar(255) | YES  |     | NULL    |                |
| category_description | varchar(255) | YES  |     | NULL    |                |
| created_at           | datetime     | NO   |     | NULL    |                |
| updated_at           | datetime     | NO   |     | NULL    |                |
| scheme_id            | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

+----------------+--------------+------+-----+---------+----------------+
| Field          | Type         | Null | Key | Default | Extra          |
+----------------+--------------+------+-----+---------+----------------+
| id             | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_id        | int(11)      | YES  | MUL | NULL    |                |
| created_at     | datetime     | NO   |     | NULL    |                |
| updated_at     | datetime     | NO   |     | NULL    |                |
+----------------+--------------+------+-----+---------+----------------+

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_point_id        | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

项目积分

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| client_id            | int(11)      | YES  |     | NULL    |                |
| category_name        | varchar(255) | YES  |     | NULL    |                |
| category_description | varchar(255) | YES  |     | NULL    |                |
| created_at           | datetime     | NO   |     | NULL    |                |
| updated_at           | datetime     | NO   |     | NULL    |                |
| scheme_id            | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

+----------------+--------------+------+-----+---------+----------------+
| Field          | Type         | Null | Key | Default | Extra          |
+----------------+--------------+------+-----+---------+----------------+
| id             | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_id        | int(11)      | YES  | MUL | NULL    |                |
| created_at     | datetime     | NO   |     | NULL    |                |
| updated_at     | datetime     | NO   |     | NULL    |                |
+----------------+--------------+------+-----+---------+----------------+

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_point_id        | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

项目

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| client_id            | int(11)      | YES  |     | NULL    |                |
| category_name        | varchar(255) | YES  |     | NULL    |                |
| category_description | varchar(255) | YES  |     | NULL    |                |
| created_at           | datetime     | NO   |     | NULL    |                |
| updated_at           | datetime     | NO   |     | NULL    |                |
| scheme_id            | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

+----------------+--------------+------+-----+---------+----------------+
| Field          | Type         | Null | Key | Default | Extra          |
+----------------+--------------+------+-----+---------+----------------+
| id             | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_id        | int(11)      | YES  | MUL | NULL    |                |
| created_at     | datetime     | NO   |     | NULL    |                |
| updated_at     | datetime     | NO   |     | NULL    |                |
+----------------+--------------+------+-----+---------+----------------+

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_point_id        | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

+----------------------------+--------------+------+-----+---------+------------

项目代码

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| client_id            | int(11)      | YES  |     | NULL    |                |
| category_name        | varchar(255) | YES  |     | NULL    |                |
| category_description | varchar(255) | YES  |     | NULL    |                |
| created_at           | datetime     | NO   |     | NULL    |                |
| updated_at           | datetime     | NO   |     | NULL    |                |
| scheme_id            | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

+----------------+--------------+------+-----+---------+----------------+
| Field          | Type         | Null | Key | Default | Extra          |
+----------------+--------------+------+-----+---------+----------------+
| id             | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_id        | int(11)      | YES  | MUL | NULL    |                |
| created_at     | datetime     | NO   |     | NULL    |                |
| updated_at     | datetime     | NO   |     | NULL    |                |
+----------------+--------------+------+-----+---------+----------------+

+----------------------+--------------+------+-----+---------+----------------+
| Field                | Type         | Null | Key | Default | Extra          |
+----------------------+--------------+------+-----+---------+----------------+
| id                   | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_point_id        | int(11)      | YES  | MUL | NULL    |                |
+----------------------+--------------+------+-----+---------+----------------+

试试这个：

ItemCode.joins(item_point: {item: :product_category}).where(product_category: {id: 1})

让我简化连接表的过程：

当您有直接关系时：

当您有间接/嵌套关系时：

试试这个

UniqueItemCode.joins(item_points: [{ items: :product_catagories }]).where(product_catagory: {id: 1})

---

你能提供你的表格结构吗？@NavjotSingh我已经更新了我的问题。@I-am-simple-user，你试过我的解决方案了吗？