Đặng Phương Nam

For multiple database connection, you need to add the following codes to the database.yml file. Here, I am giving the example of connecting two databases from a rails application

To connect multiple databases from a rails application we need to config database.yml file like this.
development:
  adapter: mysql2
  database: database1_dev
  username: dbuser
  password: dbpass
  host: localhost

development_sec:
  adapter: mysql2
  database: database2_dev
  username: dbuser
  password: dbpass
  host: localhost

production:
  adapter: mysql2
  database: database1_pro
  username: dbuser
  password: dbpass
  host: localhost

production_sec:
  adapter: mysql2
  database: database2_pro
  username: dbuser
  password: dbpass
  host: localhost

Here I have used two databases for the development and production environment.

Now we need to connect the model to databases. When you are running your application in development and production mode, all the models will be mapped through the development and production database parameters that had been mentioned in your database.yml. So for some model we need to connect to other database.

Lets assume that, we have two models User and Article. The users table is in database1_dev and database1_pro, the articles table in database2_dev and database2_pro.

Article model

class Article < ActiveRecord::Base
  establish_connection "#{Rails.env}_sec"
end

Similarly, when you adding the new migration for the second database, need to add following code to it.

class CreateArticles < ActiveRecord::Migration
  def connection
ActiveRecord::Base.establish_connection("#{Rails.env}_sec").connection
  end

  def change
    # your code goes here.
  end
end