我如何通过 ruby​​ on rails 删除表 my.sql

Question

我如何回滚或删除此公式干净我尝试 def up 和 def down 但不迁移

 class AllowAllTrackersAsSubtasks < ActiveRecord::Migration[5.1]
  def change
    trackers = Tracker.all
    trackers_ids = trackers.pluck(:id)
    trackers.each do |tracker|
      tracker.subtask_ids = trackers_ids
      tracker.save
    end
  end
end

这是另一个代码

class CreateTrackerSubtask < ActiveRecord::Migration[5.1]
  def change
    create_table "trackers_subtasks", :id => false, :force => true do |t|
      t.column "tracker_id", :integer, :default => 0, :null => false
      t.column "subtask_id", :integer, :default => 0, :null => false
      t.index [:tracker_id, :subtask_id], :unique => true
    end
  end
end

Answer 1

这段代码有效吗？？

class CreateTrackerSubtask < ActiveRecord::Migration[5.1]
  def change
    drop_table "trackers_subtasks", :id => false, :force => true do |t|
      t.column "tracker_id", :integer, :default => 0, :null => false
      t.column "subtask_id", :integer, :default => 0, :null => false
      t.index [:tracker_id, :subtask_id], :unique => true
    end
  end

还有什么代码我该怎么办？