How to implement data model correlation functionality in Ruby on Rails using MySQL

How to use MySQL to implement data model correlation function in Ruby on Rails

In Ruby on Rails development, database design and correlation are a very important part. MySQL is a commonly used relational database with powerful functions and flexible query language. It is one of the commonly used databases in Ruby on Rails. This article will introduce in detail how to use MySQL to implement the data model correlation function in Ruby on Rails, and provide code examples.

1. Data model design

Before using MySQL to implement the data model association function, we first need to design the relationship between the database table structure and the model. In MySQL, there are three commonly used relationships: one-to-one, one-to-many and many-to-many.

• One-to-one association: There is only one corresponding relationship between the two tables, such as user (User) and ID card (IDCard). One user only corresponds to one ID card, and one ID card only corresponds to Corresponds to a user.
• One-to-many association: Records in one table can correspond to multiple records in another table, such as User and Order. A user can have multiple orders, but one order can only Can belong to a user.
• Many-to-many association: There are multiple correspondences between the two tables, such as user (User) and role (Role). A user can have multiple roles, and a role can also be owned by multiple users. .

2. Create models and database migrations

In Ruby on Rails, we use the command line to create models and database migrations to define and create database tables and models. The following is a sample code for how to create a model and database migration for three relationships:

• One-to-one association:

# 创建用户模型
rails generate model User name:string
# 创建身份证模型
rails generate model IDCard number:integer

# 编辑迁移文件
class CreateIDCards < ActiveRecord::Migration[6.1]
  def change
    create_table :id_cards do |t|
      t.integer :number
      t.references :user # 添加用户外键
      t.timestamps
    end
  end
end

# 运行数据库迁移
rails db:migrate

# 编辑用户模型
class User < ApplicationRecord
  has_one :id_card # 声明一对一关联关系
end

# 编辑身份证模型
class IDCard < ApplicationRecord
  belongs_to :user # 声明一对一关联关系
end

• One-to-many association:

# 创建用户模型
rails generate model User name:string
# 创建订单模型
rails generate model Order number:integer user:references

# 编辑迁移文件
class CreateOrders < ActiveRecord::Migration[6.1]
  def change
    create_table :orders do |t|
      t.integer :number
      t.references :user # 添加用户外键
      t.timestamps
    end
  end
end

# 运行数据库迁移
rails db:migrate

# 编辑用户模型
class User < ApplicationRecord
  has_many :orders # 声明一对多关联关系
end

# 编辑订单模型
class Order < ApplicationRecord
  belongs_to :user # 声明一对多关联关系
end

• Many-to-many association:

# 创建用户模型
rails generate model User name:string
# 创建角色模型
rails generate model Role name:string

# 编辑迁移文件
class CreateRolesUsers < ActiveRecord::Migration[6.1]
  def change
    create_table :roles_users, id: false do |t|
      t.references :role
      t.references :user
    end
  end
end

# 运行数据库迁移
rails db:migrate

# 编辑用户模型
class User < ApplicationRecord
  has_and_belongs_to_many :roles # 声明多对多关联关系
end

# 编辑角色模型
class Role < ApplicationRecord
  has_and_belongs_to_many :users # 声明多对多关联关系
end

3. Data association operation

After the database association relationship is established, We can perform data association operations, such as creating related data, querying related data, updating related data, etc. The following is sample code for operating three types of associations:

• One-to-one association:

# 创建用户和身份证
user = User.create(name: "John")
id_card = IDCard.create(number: 123456, user: user)

# 查询用户的身份证
user.id_card

# 查询身份证的用户
id_card.user

• One-to-many association:

# 创建用户和订单
user = User.create(name: "John")
order1 = Order.create(number: 1, user: user)
order2 = Order.create(number: 2, user: user)

# 查询用户的订单
user.orders

# 查询订单的用户
order1.user
order2.user

• Many-to-many association:

# 创建用户和角色
user1 = User.create(name: "John")
user2 = User.create(name: "Tom")
role1 = Role.create(name: "Admin")
role2 = Role.create(name: "User")

# 建立用户和角色的关联
user1.roles << role1
user1.roles << role2
user2.roles << role2

# 查询用户的角色
user1.roles
user2.roles

# 查询角色的用户
role1.users
role2.users

Through the above code example, we can see how to use MySQL to implement the data model association function in Ruby on Rails. Whether it is a one-to-one, one-to-many or many-to-many relationship, it can be realized through the concise and powerful syntax provided by Rails. By properly designing the relationship between database table structures and models, and correctly operating associated data, we can help us build more efficient and flexible applications.

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