如何在Ruby on Rails迁移中重命名数据库列?

问题描述

我错误地将列命名为hased_password而不是hashed_password.

I wrongly named a column hased_password instead of hashed_password.

如何通过使用迁移来重命名此列来更新数据库架构?

How do I update the database schema, using migration to rename this column?

推荐答案

rename_column :table, :old_column, :new_column

您可能需要创建一个单独的迁移来执行此操作. (将FixColumnName重命名.):

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

script/generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

然后编辑迁移以执行您的意愿:

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

---

对于Rails 3.1，使用:

---

For Rails 3.1 use:

虽然up和down方法仍然适用，但是Rails 3.1接收了change方法，该方法知道如何迁移数据库并在回滚迁移时回滚它，而无需单独记录下来方法".

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

有关更多信息，请参见"活动记录迁移".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

如果您碰巧有一整列要重命名，或者需要一遍又一遍地重复表名的事情:

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

您可以使用change_table使事情保持整洁:

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

然后照常db:migrate进行操作，或者不管您从事什么业务.

Then just db:migrate as usual or however you go about your business.

对于Rails 4:

在创建用于重命名列的Migration时，Rails 4会生成一个change方法，而不是上面部分中提到的up和down.生成的change方法是:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

它将创建类似于以下内容的迁移文件:

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

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