mysql - rake 中止! StandardError : An error has occurred, 所有后续迁移均已取消:

Question

sania@sania-Swift-SF314-52:~/library$ rake db:migrate

== 20180407084831 书籍:迁移 =========================================== === -- 创建表(:书籍) rake 中止! StandardError:发生错误，所有后续迁移均已取消:

Mysql2::Error: Table 'books' already exists: CREATE TABLE `books` (`id` bigint NOT NULL AUTO_INCREMENT PRIMARY KEY, `title` varchar(32) NOT NULL, `price` float, `subject_id` int, `description` text, `created_at` timestamp NULL) ENGINE=InnoDB /home/sania/library/db/migrate/20180407084831_books.rb:4:in `up'

原因: ActiveRecord::StatementInvalid: Mysql2::Error: 表“books”已存在:CREATE TABLE books (id bigint NOT NULL AUTO_INCRMENT PRIMARY KEY, title varchar(32) NOT NULL、price float、subject_id int、description 文本、created_at 时间戳 NULL) 引擎=InnoDB /home/sania/library/db/migrate/20180407084831_books.rb:4:in `up'

原因:

Mysql2::Error: Table 'books' already exists
/home/sania/library/db/migrate/20180407084831_books.rb:4:in `up'
Tasks: TOP => db:migrate

(通过使用 --trace 运行任务查看完整跟踪)

<小时/>

这是20180407084831_books.rb文件的内容

class Books < ActiveRecord::Migration[5.1]

 def self.up
    create_table :books do |t|
         t.column :title, :string, :limit => 32, :null => false
         t.column :price, :float
         t.column :subject_id, :integer
         t.column :description, :text
         t.column :created_at, :timestamp
      end
   end

   def self.down
      drop_table :books
   end

end

<小时/>

这是20180407072616_create_books.rb文件的内容

class CreateBooks < ActiveRecord::Migration[5.1]
  def change
    create_table :books do |t|

      t.timestamps
    end
  end
end

<小时/>

请帮我解决问题。我是 Rails 新手。我也尝试过删除数据库，但 rakes 因以下错误而中止

rake 中止! ActiveRecord::NoEnvironmentInSchemaError:

架构中未找到环境数据。要解决此问题，请运行:

    bin/rails db:environment:set RAILS_ENV=development

<小时/>

我无法理解其原因。请帮我解释一下。提前致谢

Answer 1

回滚上次迁移

rake db:rollback

回滚 n 次迁移

rake db:rollback STEP=n

更多信息 here

如果您不需要上次迁移并且想要将其删除，您可以 使用@fool-dev答案