Create a new Ruby on Rails application using MySQL instead of SQLite

Normally, you would create a new Rails app using

rails ProjectName

To use MySQL, use

rails new ProjectName -d mysql

If you already have a rails project, change the adapter in the config/database.yml file to mysql and make sure you specify a valid username and password, and optionally, a socket:

development:
  adapter: mysql2
  database: db_name_dev
  username: koploper
  password:
  host: localhost
  socket: /tmp/mysql.sock

Next, make sure you edit your Gemfile to include the mysql2 or activerecord-jdbcmysql-adapter (if using jruby).

For Rails 3 you can use this command to create a new project using mysql:

$ rails new projectname -d mysql

rails -d mysql ProjectName

You should use the switch -D instead of -d because it will generate two apps and mysql with no documentation folders.

  rails -D mysql project_name  (less than version 3)

  rails new project_name -D mysql (version 3 and up)

Alternatively you just use the --database option.

If you are creating a new rails application you can set the database using the -d switch like this:

rails -d mysql myapp

Its always easy to switch your database later though, and using sqlite really is easier if you are developing on a Mac.

On new project, easy peasy:

rails new your_new_project_name -d mysql

On existing project, definitely trickier. This has given me a number of issues on existing rails projects. This kind of works with me:

# On Gemfile:
gem 'mysql2',  '>= 0.3.18', '< 0.5' # copied from a new project for rails 5.1 :)
gem 'activerecord-mysql-adapter' # needed for mysql..

# On Dockerfile or on CLI:
sudo apt-get install -y  mysql-client libmysqlclient-dev 

First make sure that mysql gem is installed, if not? than type following command in your console

gem install mysql2

Than create new rails app and set mysql database as default database by typing following command in your console

rails new app-name -d mysql

Use following command to create new app for API with mysql database

rails new <appname> --api -d mysql


  adapter: mysql2
  encoding: utf8
  pool: 5
  username: root
  password: 
  socket: /var/run/mysqld/mysqld.sock

database.yml

# MySQL. Versions 5.1.10 and up are supported.
#
# 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:
#   https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html
#
default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  host: localhost
  database: database_name
  username: username
  password: secret

development:
  <<: *default

# 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:
  <<: *default

# As with config/secrets.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read http://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
#   production:
#     url: <%= ENV['DATABASE_URL'] %>
#
production:
  <<: *default

Gemfile:

# Use mysql as the database for Active Record
gem 'mysql2', '>= 0.4.4', '< 0.6.0'

you first should make sure that MySQL driver is on your system if not run this on your terminal if you are using Ubuntu or any Debian distro

sudo apt-get install mysql-client libmysqlclient-dev

and add this to your Gemfile

gem 'mysql2', '~> 0.3.16'

then run in your root directory of the project

bundle install

after that you can add the mysql config to config/database.yml as the previous answers