我能够创建一个“rails new demoproject”并在文件夹中成功运行“rails s”，但是当我尝试使用DB“rails new demoproject -d mysql”创建一个rails项目并运行“rails” s“在文件夹中我收到以下错误：
user$ rails server
=> Booting WEBrick
=> Rails 4.0.0.beta1 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
[2013-04-20 16:06:26] INFO WEBrick 1.3.1
[2013-04-20 16:06:26] INFO ruby 1.9.3 (2013-02-22) [x86_64-darwin12.3.0]
[2013-04-20 16:06:26] INFO WEBrick::HTTPServer#start: pid=1945 port=3000
Started GET "/" for 127.0.0.1 at 2013-04-20 16:06:39 -0400
Mysql2::Error (Access denied for user 'root'@'localhost' (using password: NO)):
mysql2 (0.3.11) lib/mysql2/client.rb:44:in `connect'
mysql2 (0.3.11) lib/mysql2/client.rb:44:in `initialize'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/mysql2_adapter.rb:18:in `new'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/mysql2_adapter.rb:18:in `mysql2_connection'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:446:in `new_connection'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:456:in `checkout_new_connection'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:427:in `acquire_connection'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:364:in `block in checkout'
/Users/user/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:363:in `checkout'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:273:in `block in connection'
/Users/user/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:272:in `connection'
activerecord (4.0.0.beta1) lib/active_record/connection_adapters/abstract/connection_pool.rb:552:in `retrieve_connection'
activerecord (4.0.0.beta1) lib/active_record/connection_handling.rb:79:in `retrieve_connection'
activerecord (4.0.0.beta1) lib/active_record/connection_handling.rb:53:in `connection'
activerecord (4.0.0.beta1) lib/active_record/migration.rb:739:in `current_version'
activerecord (4.0.0.beta1) lib/active_record/migration.rb:747:in `needs_migration?'
activerecord (4.0.0.beta1) lib/active_record/migration.rb:357:in `check_pending!'
activerecord (4.0.0.beta1) lib/active_record/migration.rb:346:in `block in call'
activesupport (4.0.0.beta1) lib/active_support/logger_silence.rb:16:in `silence'
activerecord (4.0.0.beta1) lib/active_record/migration.rb:345:in `call'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.0.beta1) lib/active_support/callbacks.rb:373:in `_run__3314375952420028571__call__callbacks'
activesupport (4.0.0.beta1) lib/active_support/callbacks.rb:78:in `run_callbacks'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.0.beta1) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.0.beta1) lib/rails/rack/logger.rb:21:in `block in call'
activesupport (4.0.0.beta1) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.0.beta1) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.0.beta1) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.0.beta1) lib/rails/rack/logger.rb:21:in `call'
actionpack (4.0.0.beta1) 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.beta1) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.0.beta1) lib/action_dispatch/middleware/static.rb:64:in `call'
railties (4.0.0.beta1) lib/rails/engine.rb:510:in `call'
railties (4.0.0.beta1) lib/rails/application.rb:96: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'
/Users/user/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/Users/user/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/Users/user/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'
Rendered /Users/user/.rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.0.beta1/lib/action_dispatch/middleware/templates/rescues/_source.erb (1.0ms)
Rendered /Users/user/.rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.0.beta1/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.5ms)
Rendered /Users/user/.rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.0.beta1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.3ms)
Rendered /Users/user/.rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.0.beta1/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (51.9ms)
当我转到localhost：3000时，我在Web浏览器的标题中出现“Action Controller：Exception caught”错误，并且网页上出现了mysql2错误，可在此处查看：http://postimg.org/image/9wemvhwkj/
更新： 这是database.yml文件中的内容......
# MySQL. Versions 4.1 and 5.0 are recommended.
#
# Install the MYSQL driver
# gem install mysql2
#
# Ensure the MySQL gem is defined in your Gemfile
# gem 'mysql2'
#
# And be sure to use new-style password hashing:
# http://dev.mysql.com/doc/refman/5.0/en/old-client.html
development:
adapter: mysql2
encoding: utf8
database: cms_development
pool: 5
username: root
password:
socket: /tmp/mysql.sock
# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
adapter: mysql2
encoding: utf8
database: cms_test
pool: 5
username: root
password:
socket: /tmp/mysql.sock
production:
adapter: mysql2
encoding: utf8
database: cms_production
pool: 5
username: root
password:
socket: /tmp/mysql.sock
答案 0 :(得分：1)
database.yml文件中的用户名和密码无权访问数据库
答案 1 :(得分：0)
Mysql2::Error (Access denied for user 'root'@'localhost' (using password: NO)): - 检查数据库用户名\密码
答案 2 :(得分：0)
我和你们的帮助解决了我的问题：
在终端中键入：mysql -u root -p（如果你在安装mysql时没有设置root密码，则没有-p）
然后键入CREATE DATABASE cms_development;（用您的rails项目名称替换cms）
然后打开位于rails项目文件夹
中的config / database.yml在“开发：”下输入“password：”
下的密码