我想创建外键,但我无法创建它们(teacher_id,course_id 的外键)。
请查看代码 - 我应该更改什么来生成外键?
案例应用=学校
脚步:
安慰:
rails new school
rails g model teacher name:string
rails g model course name:string
rails g model teachercourse teacher_id:integer course_id:integer
向模型添加代码:
class Course < ActiveRecord::Base
attr_accessible :name
has_many :teachers, through: :teachercourse
end
class Teacher < ActiveRecord::Base
attr_accessible :name
has_many :courses, through: :teachercourse
end
class Teachercourse < ActiveRecord::Base
attr_accessible :course_id, :teacher_id
belongs_to :course
belongs_to :teacher
end
向迁移添加代码:
class CreateTeachercourses < ActiveRecord::Migration
def change
create_table :teachercourses do |t|
t.integer :teacher_id
t.integer :course_id
t.timestamps
end
add_index :teacher_id
add_index :course_id
end
end
安慰:
rake db:migrate
rake db:schema:load
mysql db innodb 部分转储(teacher_id、course_id 没有外键):
CREATE TABLE IF NOT EXISTS `courses` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`created_at` datetime NOT NULL,
`updated_at` datetime NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;
CREATE TABLE IF NOT EXISTS `teachercourses` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`teacher_id` int(11) DEFAULT NULL,
`course_id` int(11) DEFAULT NULL,
`created_at` datetime NOT NULL,
`updated_at` datetime NOT NULL,
PRIMARY KEY (`id`),
KEY `index_teachercourses_on_course_id` (`course_id`),
KEY `index_teachercourses_on_teacher_id` (`teacher_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;
CREATE TABLE IF NOT EXISTS `teachers` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`created_at` datetime NOT NULL,
`updated_at` datetime NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;