我得到的错误如下：
C：/Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-ming32/lib/mysql2/mysql2.rb:2：在require'中：无法加载这样的文件--mysql2/2.2/mysql2（LoadError）来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2/mysql2.rb:2:in'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2.rb:31:in require'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/mysql2-0.3.18-x64-mingw32/lib/mysql2.rb:31:in'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler/runtime.rb:76:in require'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler/runtime.rb:76:在require'中的块（2个级别）中来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler/runtime.rb:72:in each'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler/runtime.rb:72:require中的块来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler/runtime.rb:61:in each'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler/runtime.rb:61:in require'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/bundler-1.9.1/lib/bundler.rb:134:需要来自D:/xamplep/htdocs/RubyCms/config/application.rb:7:in'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:78:in require'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:78：在服务器中的块中来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:75:in tap'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:75:在服务器中来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:39:in run_command！'来自C:\Ruby22-x64/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands.rb:17:in'从垃圾箱/轨道：4:需要从箱子/轨道：4:in’
我真的不知道怎么了。
如有任何帮助，我们将不胜感激。
当我意外地用默认数据库（sqlite3）创建了一个新的Rails应用程序，但实际上安装了mysql2时，我也遇到了同样的错误。
检查您安装了哪个数据库，gemfile中需要哪个数据库。