Ruby on rails mysql problem

I'm creating my first ROR application. Details:

creating new app ->

rails new simple_cms -d mysql

creating a controller and a corresponding view -->

rails generate controller demo index

Then when after i started the rails server, the http://localhost:3000 page works perfectly fine. but when i try to go to the page that I just created, http://localhost:3000/demo/index, it spurts out a MYSQL error:

Access denied for user 'root'@'localhost' (using pass开发者_如何学运维word: NO) 

At first, I think it's just a database connection problem, so I've gone through the MYSQL interface and create a new database called: simple_cms_development and I have also made a corresponding user: simple_cms with granted privileges.

and lastly, I have configured the database.yml file to fit the details:

development:
  adapter: mysql
  encoding: utf8
  reconnect: false
  database: simple_cms_development
  pool: 5
  username: simple_cms
  password: developer
  host: localhost

But still, it spits out the same mysql problem: Access denied for user 'root'@'localhost' (using password: NO)

Please. to anyone who knows how to use mysql as a database for rails app..A help would be really appreciated. Thank you so much!

UPDATE: This is all what's inside on the database.yml file

# MySQL.  Versions 4.1 and 5.0 are recommended.
#
# Install the MySQL driver:
#   gem install mysql2
#
# And be sure to use new-style password hashing:
#   http://dev.mysql.com/doc/refman/5.0/en/old-client.html
development:
  adapter: mysql
  encoding: utf8
  reconnect: false
  database: simple_cms_development
  pool: 5
  username: root
  password: developer
  host: localhost

# 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: mysql2
  encoding: utf8
  reconnect: false
  database: simple_cms_test
  pool: 5
  username: root
  password:
  host: localhost

production:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: simple_cms_production
  pool: 5
  username: root
  password:
  host: localhost

I found that you need to add the following line to config/database.yml:

host: localhost

production:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  host: your_host # <----- normally localhost
  database: the_db_I_made
  pool: 5
  username: the_user_I_made
  password: the_password
  socket: /var/lib/mysql/mysql.sock

Only reason that can cause your issue is that you are loading your server with different environment. I think that in your case you are loading your server under production mode.