How to implement “Multiple Database(DB) Connection” in Rails3?

In some scenarios we need data from a external database to execute in different application.

Here, we need a bridge which will connect these two different databases. In Ruby on Rails this

can be achieved through ActiveRecord’s establish_connection(). Following are the steps to

create a rails application which uses multiple database, where the existing database and the

external database will work simultaneously.

Let's say there are two different rails application say “myapp” and “remoteapp” where “myapp”

depends upon “remoteapp” user table.

Step#1

Edit the 'database.yml' file for the 'myapp' project

Add a new connection for 'remoteapp' as below:

# Connection name, it will be used to connect from myappconnect_remote: adapter: mysql2 username: user_name # username of the remoteapp database password: password # password of the remoteapp database pool: 5 database: remoteapp_db_name # database name of the remoteapp host: www.remoteapphost.com # host name of the db

Step#2

In models folder create a new file called user.rb if it is not already there. Write below code to

establish connection with remote app's database.

class User < ActiveRecord::Base establish_connection("connect_remote")end

Here use the connection name defined in the database.yml file in the establish_connection()

method.

Like this you can create models to connect with remote databases.

Step#3

It will give you the flexibility for managing users data of remote app's database like it is present in

the myapp database.

Use the normal way to get data from the users table like

User.all #To get all the recordsUser.find(id) #To get required record

Here you can also insert or update data in users table by normal way as it is present in myapp

application

#insert new recorduser = User.new params[:user]user.save

#update existing recorduser = User.find params[:id]user.update_attributes(params[:user])