红宝石在Rails上的MySQL错误新的应用程序数据库未知

Question

我已经在mysql的路径上安装了ruby。

我使用命令安装了mysql

 sudo apt-get install mysql-server

出现提示要求输入密码的提示，我将其设置为1234，再次提示确认密码出现。

我还使用安装了mysql2 gem

gem install mysql2

并使用创建了一个新的Rails应用

rails new app -d mysql

新应用已成功创建，但是当我使用rails server启动rails server并打开http://localhost:3000 ，发生了错误：

unknown database

整个堆栈跟踪如下所示

mysql2 (0.3.14) lib/mysql2/client.rb:67:in `connect'
mysql2 (0.3.14) lib/mysql2/client.rb:67:in `initialize'
activerecord (4.0.0) lib/active_record/connection_adapters/mysql2_adapter.rb:18:in `new'
activerecord (4.0.0) lib/active_record/connection_adapters/mysql2_adapter.rb:18:in `mysql2_connection'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:440:in `new_connection'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:450:in `checkout_new_connection'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:421:in `acquire_connection'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:356:in `block in checkout'
/home/sana/.rvm/rubies/ruby-2.0.0-p353/lib/ruby/2.0.0/monitor.rb:211:in `mon_synchronize'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:355:in `checkout'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:265:in `block in connection'
/home/sana/.rvm/rubies/ruby-2.0.0-p353/lib/ruby/2.0.0/monitor.rb:211:in `mon_synchronize'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:264:in `connection'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:546:in `retrieve_connection'
activerecord (4.0.0) lib/active_record/connection_handling.rb:79:in `retrieve_connection'
activerecord (4.0.0) lib/active_record/connection_handling.rb:53:in `connection'
activerecord (4.0.0) lib/active_record/query_cache.rb:51:in `restore_query_cache_settings'
activerecord (4.0.0) lib/active_record/query_cache.rb:43:in `rescue in call'
activerecord (4.0.0) lib/active_record/query_cache.rb:32:in `call'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.0) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.0) lib/active_support/callbacks.rb:373:in `_run__695031866633904995__call__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `block in call'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.0) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/static.rb:64:in `call'
railties (4.0.0) lib/rails/engine.rb:511:in `call'
railties (4.0.0) lib/rails/application.rb:97:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
/home/sana/.rvm/rubies/ruby-2.0.0-p353/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
/home/sana/.rvm/rubies/ruby-2.0.0-p353/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
/home/sana/.rvm/rubies/ruby-2.0.0-p353/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'

错误在哪里？

config/database.yml

development:
  adapter: mysql2
  encoding: utf8
  database: mysqltestapp_development
  pool: 5
  username: root
  password: 1234
  host: 127.0.0.1
  socket: /var/run/mysqld/mysqld.sock

Answer 1

假设错误消息类似于

发生未知数据库错误

这意味着该数据库不存在。 确保在MySQL中创建了它（Rails不会自动创建它）。

mysql -e 'create database mysqltestapp_development;'

如果应用不是新应用，则还应该加载架构。

rake db:schema:load