title: Gem::LoadError: Add `gem 'mysql'` to your Gemfile
body: <pre><code>Gem::LoadError: Specified 'mysql' for database adapter, but the gem is not loaded. Add `gem 'mysql'` to your Gemfile.
  </code></pre>
  
  <p>I have been getting this error when I was following this guide: 
   <a href="http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html" rel="nofollow">http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html</a>
  and running </p>
  
  <pre><code>$ cd activerecord
  $ bundle exec rake test_sqlite3
  </code></pre>
  
  <p>After searching around for a bit, I've been told I need to modify the <code>Gemfile</code> and add <code>gem 'mysql'</code> then run <code>bundle install</code>. However, I am not able to see mysql in the list. </p>
  
  <pre><code>Resolving dependencies...
  Using rake (10.1.0) 
  Using i18n (0.6.5) 
  Using json (1.8.0) 
  Using minitest (5.0.8) 
  Using atomic (1.1.14) 
  Using thread_safe (0.1.3) 
  Using tzinfo (0.3.38) 
  Using activesupport (4.1.0.beta) from source at . 
  Using rack (1.5.2) 
  Using rack-test (0.6.2) 
  Using actionpack (4.1.0.beta) from source at . 
  Using builder (3.1.4) 
  Using activemodel (4.1.0.beta) from source at . 
  Using erubis (2.7.0) 
  Using actionview (4.1.0.beta) from source at . 
  Using mime-types (1.25) 
  Using polyglot (0.3.3) 
  Using treetop (1.4.15) 
  Using mail (2.5.4) 
  Using actionmailer (4.1.0.beta) from source at . 
  Using arel (4.0.0) 
  Using activerecord (4.1.0.beta) from source at . 
  Using bcrypt-ruby (3.1.2) 
  Using benchmark-ips (1.2.0) 
  Using bundler (1.3.5) 
  Using coffee-script-source (1.6.3) 
  Using execjs (2.0.2) 
  Using coffee-script (2.2.0) 
  Using thor (0.18.1) 
  Using railties (4.1.0.beta) from source at . 
  Using coffee-rails (4.0.0) 
  Using columnize (0.3.6) 
  Using dalli (2.6.4) 
  Using debugger-linecache (1.2.0) 
  Using debugger-ruby_core_source (1.2.3) 
  Using debugger (1.6.2) 
  Using hike (1.2.3) 
  Using jquery-rails (2.2.2) 
  Using mustache (0.99.4) 
  Using mini_portile (0.5.1) 
  Using nokogiri (1.6.0) 
  Using kindlerb (0.1.1) 
  Using metaclass (0.0.1) 
  Using mocha (0.14.0) 
  Using multi_json (1.8.1) 
  Using racc (1.4.9) 
  Using rack-cache (1.2) 
  Using tilt (1.4.1) 
  Using sprockets (2.10.0) 
  Using sprockets-rails (2.0.0) 
  Using rails (4.1.0.beta) from source at . 
  Using rdoc (3.12.2) 
  Using redcarpet (2.2.2) 
  Using sdoc (0.3.20) 
  Using sqlite3 (1.3.8) 
  Using turbolinks (1.3.0) 
  Using uglifier (2.2.1) 
  Using w3c_validators (1.2) 
  Using yajl-ruby (1.1.0) 
  Your bundle is complete!
  Gems in the group db were not installed.
  Use `bundle show [gemname]` to see where a bundled gem is installed.
  </code></pre>
  
  <p><strong>Gemfile</strong></p>
  
  <pre><code>source 'https://rubygems.org'
  
  gem 'rails',     path: '/home/terence/rails'
  gem 'arel',      github: 'rails/arel'
  
  gem 'mysql', '~&gt; 2.9.1'
  gem 'mysql2', '~&gt; 0.3.13'
  
  # Use sqlite3 as the database for Active Record
  gem 'sqlite3'
  
  # Use edge version of sprockets-rails
  gem 'sprockets-rails', github: 'rails/sprockets-rails'
  
  # Use SCSS for stylesheets
  gem 'sass-rails', github: 'rails/sass-rails'
  
  # Use Uglifier as compressor for JavaScript assets
  gem 'uglifier', '&gt;= 1.3.0'
  
  # Use CoffeeScript for .js.coffee assets and views
  gem 'coffee-rails', github: 'rails/coffee-rails'
  
  # See https://github.com/sstephenson/execjs#readme for more supported runtimes
  # gem 'therubyracer', platforms: :ruby
  
  # Use jquery as the JavaScript library
  gem 'jquery-rails'
  
  # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
  gem 'turbolinks'
  
  # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
  gem 'jbuilder', '~&gt; 1.2'
  
  # Run `rails console` in the browser. Read more: https://github.com/rails/web-console
  gem 'web-console', group: :development
  
  group :doc do
    # bundle exec rake doc:rails generates the API under doc/api.
    gem 'sdoc', require: false
  end
  
  # Use ActiveModel has_secure_password
  # gem 'bcrypt-ruby', '~&gt; 3.1.2'
  
  # Use unicorn as the app server
  # gem 'unicorn'
  
  # Use Capistrano for deployment
  # gem 'capistrano', group: :development
  
  # Use debugger
  # gem 'debugger', group: [:development, :test]
  </code></pre>
  
  <p>But, if I run <code>gem list</code>, my output is the following: </p>
  
  <pre><code>*** LOCAL GEMS ***
  
  actionmailer (4.0.0)
  actionpack (4.0.0)
  activemodel (4.0.0)
  activerecord (4.0.0)
  activerecord-deprecated_finders (1.0.3)
  activesupport (4.0.0)
  arel (4.0.0)
  atomic (1.1.14)
  bcrypt-ruby (3.1.2)
  benchmark-ips (1.2.0)
  builder (3.1.4)
  bundler (1.3.5)
  bundler-unload (1.0.2)
  celluloid (0.15.2)
  chunky_png (1.2.8)
  coderay (1.0.9)
  coffee-rails (4.0.0)
  coffee-script (2.2.0)
  coffee-script-source (1.6.3)
  columnize (0.3.6)
  compass (0.12.2)
  cyaml (0.0.45)
  dalli (2.6.4)
  debugger (1.6.2)
  debugger-linecache (1.2.0)
  debugger-ruby_core_source (1.2.3)
  em-websocket (0.5.0)
  erubis (2.7.0)
  eventmachine (1.0.3)
  execjs (2.0.2)
  executable-hooks (1.2.3)
  ffi (1.9.0)
  formatador (0.2.4)
  fssm (0.2.10)
  guard (2.0.3)
  guard-compass (1.0.0)
  guard-haml (1.1.0)
  guard-livereload (2.0.0)
  haml (4.0.3)
  hike (1.2.3)
  http_parser.rb (0.5.3)
  i18n (0.6.5)
  jbuilder (1.5.1)
  jquery-rails (3.0.4, 2.2.2)
  json (1.8.0)
  kindlerb (0.1.1)
  listen (2.0.1)
  lumberjack (1.0.4)
  mail (2.5.4)
  metaclass (0.0.1)
  method_source (0.8.2)
  mime-types (1.25)
  mini_portile (0.5.1)
  minitest (5.0.8, 4.7.5)
  mocha (0.14.0)
  multi_json (1.8.1)
  mustache (0.99.4)
  mysql (2.9.1)
  mysql2 (0.3.13)
  nokogiri (1.6.0)
  polyglot (0.3.3)
  pry (0.9.12.2)
  racc (1.4.9)
  rack (1.5.2)
  rack-cache (1.2)
  rack-test (0.6.2)
  rails (4.0.0)
  railties (4.0.0)
  rake (10.1.0)
  rb-fsevent (0.9.3)
  rb-inotify (0.9.2)
  rdoc (3.12.2)
  redcarpet (2.2.2)
  rubygems-bundler (1.3.4)
  rvm (1.11.3.8)
  sass (3.2.12)
  sass-rails (4.0.0)
  sdoc (0.3.20)
  slop (3.4.6)
  sprockets (2.10.0)
  sprockets-rails (2.0.0)
  sqlite3 (1.3.8)
  thor (0.18.1)
  thread_safe (0.1.3)
  tilt (1.4.1)
  timers (1.1.0)
  treetop (1.4.15)
  turbolinks (1.3.0)
  tzinfo (0.3.38, 0.3.37)
  uglifier (2.2.1)
  w3c_validators (1.2)
  web-console (1.0.3)
  yajl-ruby (1.1.0)
  </code></pre>
  
  <p><strong>database.yml</strong></p>
  
  <pre><code># SQLite version 3.x
  #   gem install sqlite3
  #
  #   Ensure the SQLite 3 gem is defined in your Gemfile
  #   gem 'sqlite3'
  development:
    adapter: sqlite3
    database: db/development.sqlite3
    pool: 5
    timeout: 5000
  
  # 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: sqlite3
    database: db/test.sqlite3
    pool: 5
    timeout: 5000
  
  production:
    adapter: sqlite3
    database: db/production.sqlite3
    pool: 5
    timeout: 5000
  </code></pre>
  
  <p>Help please?</p>