尝试更新gem（邮箱）并将其删除后，我收到此错误。
Mysql2 ::错误：表'对话'已经存在：CREATE TABLE conversations（id int（11）DEFAULT NULL auto_increment PRIMARY KEY，subject varchar（255）DEFAULT'' ，created_at datetime NOT NULL，updated_at datetime NOT NULL）
我试过了：
我不想丢失我的数据并放弃表格。 有什么想法吗？
更新
Rake db:migrate:status
up 20140526010413 Adduserfollowme to users
up 20140703193119 Add vote weight to votes
up 20140713211140 Add partime to user
up 20140716024440 Add devise to admin users
up 20140716024510 Create active admin comments
up 20140727042518 ********** NO FILE **********
up 20140727051902 Add slug to activities
down 20140728031732 Create mailboxer.mailboxer engine
down 20140728031733 Add notified object.mailboxer engine
down 20140728031734 Add notification code.mailboxer engine
down 20140728031735 Add attachments.mailboxer engine
down 20140728031736 Rename receipts read.mailboxer engine
down 20140728031737 Add global notification support.mailboxer engine
rake db:rollback
== AddSlugToActivities: reverting ============================================
-- remove_index("activities", {:column=>:slug})
-> 0.0215s
-- remove_column("activities", :slug)
-> 0.0342s
== AddSlugToActivities: reverted (0.0559s) ===================================
Rake db:migrate
== AddSlugToActivities: migrating ============================================
-- add_column(:activities, :slug, :string)
-> 0.0266s
-- add_index(:activities, :slug)
-> 0.0104s
== AddSlugToActivities: migrated (0.0373s) ===================================
== CreateMailboxer: migrating ================================================
-- create_table(:conversations)
rake aborted!
StandardError: An error has occurred, all later migrations canceled:
Mysql2::Error: Table 'conversations' already exists: CREATE TABLE `conversations` (`id` int(11) DEFAULT NULL auto_increment PRIMARY KEY, `subject` varchar(255) DEFAULT '', `created_at` datetime NOT NULL, `updated_at` datetime NOT NULL) ENGINE=InnoDB/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:243:in `query'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:243:in `block in execute'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract_adapter.rb:280:in `block in log'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activesupport-3.2.12/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract_adapter.rb:275:in `log'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:243:in `execute'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/mysql2_adapter.rb:211:in `execute'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract/schema_statements.rb:170:in `create_table'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/foreigner-1.6.1/lib/foreigner/connection_adapters/abstract/schema_statements.rb:14:in `create_table'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:432:in `create_table'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:466:in `block in method_missing'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:438:in `block in say_with_time'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:438:in `say_with_time'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:458:in `method_missing'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:334:in `method_missing'
/home/bill/apps/woomatch/releases/20140728100705/db/migrate/20140728031732_create_mailboxer.mailboxer_engine.rb:6:in `up'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:370:in `up'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:410:in `block (2 levels) in migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:410:in `block in migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/connection_adapters/abstract/connection_pool.rb:129:in `with_connection'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:389:in `migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:528:in `migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:720:in `block (2 levels) in migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:777:in `call'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:777:in `ddl_transaction'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:719:in `block in migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:700:in `each'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:700:in `migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:570:in `up'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/migration.rb:551:in `migrate'
/home/bill/apps/woomatch/shared/bundle/ruby/1.9.1/gems/activerecord-3.2.12/lib/active_record/railties/databases.rake:179:in `block (2 levels) in <top (required)>'
Tasks: TOP => db:migrate
接下来我该怎么做？
答案 0 :(得分：1)
没有rake db:migrate rollback，只有rake db:rollback
尝试使用rake db:migrate:status，然后使用rake db:rollback使不需要的迁移失效。
有时候，当“出现问题”并且你们进行了大量的迁移回滚时，有必要对某些行进行注释，进行迁移\回滚并再次对其进行修改。
如果它不起作用，请尝试显示失败的迁移代码