Before starting with this chapter, make sure your database server is setup and running. Ruby on Rails recommends to create three databases – a database each for development, testing, and production environment. According to convention, their names should be as follows −

• library_development
• library_production
• library_test

You should initialize all three of them and create a username and password for them with full read and write privileges. We are using root user ID for our application. In MySQL, a console session looks as follows −

mysql> create database library_development;
Query OK, 1 row affected (0.01 sec)

mysql> use library_development;
Database changed

mysql> grant all privileges on library_development.* 
   to ''root''@''localhost'' identified by ''password'';
Query OK, 0 rows affected (0.00 sec)

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

You can do the same thing for the other two databases, library_production and library_test.

Configuring database.yml

At this point, you need to let Rails know about the username and password for the databases. You do this in the file database.yml, available in the C:rubylibraryconfig subdirectory of Rails Application you created. This file has live configuration sections for MySQL databases. In each of the sections you use, you need to change the username and password lines to reflect the permissions on the databases you”ve created.

When you finish, it should look something like −

development:
  adapter: mysql
  encoding: utf8
  database: library_development
  username: root
  password: password
  host: localhost
test:
  adapter: mysql
  encoding: utf8
  database: library_test
  username: root
  password: password
  host: localhost
production:
  adapter: mysql
  encoding: utf8
  database: library_production
  username: root
  password: password
  host: localhost

NOTE − You can use similar setting for other databases if you are using any other database except MySQL.

What is Next?

The next two chapters explain how to model your database tables and how to manage those using Rails Migrations.