问题描述
我有以下迁移文件 db\migrate\20100905201547_create_blocks.rb
如何具体回滚该迁移文件？
How can I specifically rollback that migration file?
推荐答案
rake db:rollback STEP=1
如果要回滚的迁移是最后一次应用，则是一种方法。您可以用1代替要返回的许多迁移。
Is a way to do this, if the migration you want to rollback is the last one applied. You can substitute 1 for however many migrations you want to go back.
例如：
rake db:rollback STEP=5
还将回滚发生的所有迁移稍后（4、3、2和1）。
Will also rollback all the migration that happened later (4, 3, 2 and also 1).
要将所有迁移回滚到（包括）目标迁移，请使用：（已添加此更正的命令在所有评论指出原始帖子中的错误之后）
To roll back all migrations back to (and including) a target migration, use: (This corrected command was added AFTER all the comments pointing out the error in the original post)
rake db:migrate VERSION=20100905201547
为了回滚仅一个特定的迁移（无序），请使用：
In order to rollback ONLY ONE specific migration (OUT OF ORDER) use:
rake db:migrate:down VERSION=20100905201547
请注意，这不会回滚任何中间的迁移-仅列出其中的一个。如果这不是您想要的，则可以安全地运行 rake db：migrate ，它将仅重新运行该命令，而跳过以前未回滚的其他命令。
Note that this will NOT rollback any interceding migrations -- only the one listed. If that is not what you intended, you can safely run rake db:migrate and it will re-run only that one, skipping any others that were not previously rolled back.
如果您想按顺序迁移单个迁移，则还有一个相反的 db：migrate：up ：
And if you ever want to migrate a single migration out of order, there is also its inverse db:migrate:up:
rake db:migrate:up VERSION=20100905201547
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