如何重置轨道中的单个表？
我想要主键值从1开始。
要重置SQLite中的索引/主键，只需键入：
$ rails console > ActiveRecord::Base.connection.execute("DELETE from sqlite_sequence where name = 'yourtablename'") 很多人（像我）来这里find如何删除表中的所有数据。 干得好：
$ rails console > ModelName.delete_all
要么
> ModelName.destroy_all
destroy_all检查依赖关系和callback，并花费更长的时间。 delete_all是一个直接的SQL查询。
更多信息在这里： http : //apidock.com/rails/ActiveRecord/Base/delete_all/class
我一直在使用以下从rails控制台删除表中的所有内容，然后重置索引计数器（Ruby 2＆Rails 4）：
> ModelName.delete_all > ActiveRecord::Base.connection.reset_pk_sequence!('plural_model_name')
@ khelll的链接是有帮助的。 您要截断一个表的命令是：
ActiveRecord::Base.connection.execute("TRUNCATE #{table_name}")
将gem'database_cleaner gem 'database_cleaner'添加到您的Gemfile中，运行$ bundle install ，然后：
> DatabaseCleaner.clean_with(:truncation, :only => ['yourtablename'])
你可以指定更多的表格：
> DatabaseCleaner.clean_with(:truncation, :only => ['table1', 'table2', 'table3'])
如果你离开最后一个参数，它会截断整个数据库：
> DatabaseCleaner.clean_with(:truncation) # your database is truncated
我正在使用Rails 4.2.0和Sqlite3
以下是对我有用的东西（从以上所有内容中抽取一点）：
$ rails c > ModelName.delete_all > ActiveRecord::Base.connection.execute("DELETE from sqlite_sequence where name = 'table_name'")
然后，我可以添加新的logging到我的表，索引从1开始
我不认为你能做到这一点。 但是，你可以写自己的耙子任务
有关您的信息，可以通过执行以下操作获取可用的rake任务列表：
rake --tasks
你会得到像这样的东西：
rake backups:clear # Cleanup Backup files rake clear # Cleanup temporary, log and backup files rake db:fixtures:load # Load fixtures into the current environment's database. Load specific fixtures using FIXTURES=x,y rake db:migrate # Migrate the database through scripts in db/migrate. Target specific version with VERSION=x rake db:schema:dump # Create a db/schema.rb file that can be portably used against any DB supported by AR rake db:schema:load # Load a schema.rb file into the database rake db:sessions:clear # Clear the sessions table rake db:sessions:create # Creates a sessions table for use with CGI::Session::ActiveRecordStore rake db:structure:dump # Dump the database structure to a SQL file rake db:test:clone # Recreate the test database from the current environment's database schema rake db:test:clone_structure # Recreate the test databases from the development structure rake db:test:prepare # Prepare the test database and load the schema rake db:test:purge # Empty the test database rake doc:app # Build the app HTML Files rake doc:clobber_app # Remove rdoc products rake doc:clobber_plugins # Remove plugin documentation rake doc:clobber_rails # Remove rdoc products rake doc:plugins # Generate documation for all installed plugins rake doc:rails # Build the rails HTML Files rake doc:reapp # Force a rebuild of the RDOC files rake doc:rerails # Force a rebuild of the RDOC files rake log:clear # Truncates all *.log files in log/ to zero bytes rake rails:freeze:edge # Lock to latest Edge Rails or a specific revision with REVISION=X (ex: REVISION=4021) or a tag with TAG=Y (ex: TAG=rel_1-1-0) rake rails:freeze:gems # Lock this application to the current gems (by unpacking them into vendor/rails) rake rails:unfreeze # Unlock this application from freeze of gems or edge and return to a fluid use of system gems rake rails:update # Update both configs, scripts and public/javascripts from Rails rake rails:update:configs # Update config/boot.rb from your current rails install rake rails:update:javascripts # Update your javascripts from your current rails install rake rails:update:scripts # Add new scripts to the application script/ directory rake stats # Report code statistics (KLOCs, etc) from the application rake test # Test all units and functionals rake test:functionals # Run the functional tests in test/functional rake test:integration # Run the integration tests in test/integration rake test:plugins # Run the plugin tests in vendor/plugins/**/test (or specify with PLUGIN=name) rake test:recent # Test recent changes rake test:uncommitted # Test changes since last checkin (only Subversion) rake test:units # Run the unit tests in test/unit rake tmp:assets:clear # Clears all files in tmp/test/assets rake tmp:cache:clear # Clears all files and directories in tmp/cache rake tmp:clear # Clear session, cache, and socket files from tmp/ rake tmp:create # Creates tmp directories for sessions, cache, and sockets rake tmp:pids:clear # Clears all files in tmp/pids rake tmp:sessions:clear # Clears all files in tmp/sessions rake tmp:sockets:clear # Clears all files in tmp/sockets
通过
看看这里 ，你仍然可能需要一些定制来截断一个特定的表。
由于Rails 4.2可以直接在ActiveRecord连接上使用truncate ：
ActiveRecord::Base.connection.truncate(:table_name)
这将擦除所有数据并重置表中的自动增量计数器 。 在MySQL和Postgres 中工作，在Sqlite中不起作用。
对于在数据库是Postgres的时候寻找这个问题的答案的其他人，你可以从Rails控制台执行：
rails console irb(main):028:0> ActiveRecord::Base.connection.execute("SELECT SETVAL('accounts_id_seq', 1)")
accounts中的accounts_id_seq是表的名称。
