Ruby on Rails 数据库迁移不在 MySQL 表中创建外键

Ruby on Rails database migration not creating foreign keys in MySQL tables(Ruby on Rails 数据库迁移不在 MySQL 表中创建外键)

问题描述

我正在尝试在 Ruby on Rails 应用程序中修改数据库迁移.我使用 MySQL 作为我的数据库，并希望将外键添加到正在创建的表中.我正在使用以下代码，并且在遵循在适当列上创建空值的规范时，没有应用外键约束.

I am trying to modify a database Migration in a Ruby on Rails application. I am using MySQL as my database and would like to add foreign keys to the table that is being created. I am using the following code and while the specifications for creating null values on appropriate columns is being followed no foreign key constraints are being applied.

class CreateBookCheckOuts < ActiveRecord::Migration
  def self.up
    create_table :book_check_outs do |t|
      t.integer :book_id, :null => false, :options =>
        "CONSTRAINT fk_book_check_out_books REFERENCES books(id)"
      t.integer :person_id, :null => false, :options =>
        "CONSTRAINT fk_book_check_out_people REFERENCES people(id)"
      t.datetime :OutDate, :null => false
      t.datetime :ReturnDate, :null => true

      t.timestamps
    end
  end

  def self.down
    drop_table :book_check_outs
  end
end

推荐答案

你可以使用 Foreigner宝石.

然后将您的迁移更改为:

Then change your migration to this:

class CreateBookCheckOuts < ActiveRecord::Migration
  def self.up
    create_table :book_check_outs do |t|
      t.integer :book_id, :null => false
      t.integer :person_id, :null => false
      t.datetime :OutDate, :null => false
      t.datetime :ReturnDate, :null => true

      t.timestamps
    end
    add_foreign_key(:book_check_outs, :books)
    add_foreign_key(:book_check_outs, :people)
  end

  def self.down
    remove_foreign_key(:book_check_outs, :books)
    remove_foreign_key(:book_check_outs, :people)
    drop_table :book_check_outs
  end
end

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