打开rails控制台

ActiveRecord::Base.connection.execute("drop table table_name")

手动编写迁移。例如:运行rails g migration DropUsers。

至于迁移的代码，我将引用Maxwell Holder的帖子Rails migration Checklist

BAD—运行rake db:migrate and then rake db:rollback将失败

class DropUsers < ActiveRecord::Migration
  def change
    drop_table :users
  end
end

GOOD -揭示了迁移不应该可逆的意图

class DropUsers < ActiveRecord::Migration
  def up
    drop_table :users
  end

  def down
    fail ActiveRecord::IrreversibleMigration
  end
end

BETTER -实际上是可逆的

class DropUsers < ActiveRecord::Migration
  def change
    drop_table :users do |t|
      t.string :email, null: false
      t.timestamps null: false
    end
  end
end

我需要删除我们的迁移脚本以及表本身……

class Util::Table < ActiveRecord::Migration

 def self.clobber(table_name)   
    # drop the table
    if ActiveRecord::Base.connection.table_exists? table_name
      puts "\n== " + table_name.upcase.cyan + " ! " 
           << Time.now.strftime("%H:%M:%S").yellow
      drop_table table_name 
    end

    # locate any existing migrations for a table and delete them
    base_folder = File.join(Rails.root.to_s, 'db', 'migrate')
    Dir[File.join(base_folder, '**', '*.rb')].each do |file|
      if file =~ /create_#{table_name}.rb/
        puts "== deleting migration: " + file.cyan + " ! "
             << Time.now.strftime("%H:%M:%S").yellow
        FileUtils.rm_rf(file)
        break
      end
    end
  end

  def self.clobber_all
    # delete every table in the db, along with every corresponding migration 
    ActiveRecord::Base.connection.tables.each {|t| clobber t}
  end

end

从终端窗口运行:

$ rails runner "Util::Table.clobber 'your_table_name'"

or

$ rails runner "Util::Table.clobber_all"

帮助文档

在迁移中，您可以通过以下方式删除表:

drop_table(table_name, **options)

选项:

:力 设置为:cascade也可以删除依赖对象。默认为false

: if_exists 设置为true仅在表存在时删除它。默认为false

例子:

Create migration for drop table, for example we are want to drop User table rails g migration DropUsers Running via Spring preloader in process 13189 invoke active_record create db/migrate/20211110174028_drop_users.rb Edit migration file, in our case it is db/migrate/20211110174028_drop_users.rb class DropUsers < ActiveRecord::Migration[6.1] def change drop_table :users, if_exist: true end end Run migration for dropping User table rails db:migrate == 20211110174028 DropUsers: migrating =============================== -- drop_table(:users, {:if_exist=>true}) -> 0.4607s

执行命令:-

rails g migration drop_table_name

然后:

rake db:migrate

或者如果你使用的是MySql数据库，那么:

登录数据库 显示数据库; 显示表; table_name下降;

ActiveRecord:: Base.connection。drop_table: table_name