Adding column to rails table - ruby-on-rails

Question

I am running rails 1.9.3 and I wanted to add a column to an already migrated table.I tried the following:
Firstly I just edited the migrate file and added my field and ran the rake db:migrate command only to see the following error:
NameError: undefined local variable or method `migrate' for main:Object
from (irb):13
from /Users/praveenmody/.rvm/gems/ruby-1.9.3-p448/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
from /Users/praveenmody/.rvm/gems/ruby-1.9.3-p448/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
from /Users/praveenmody/.rvm/gems/ruby-1.9.3-p448/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
Next I tried running the following command from the rails console:
rails generate migration add_place_to_coordinates place:string
only to recieve the following error:
NameError: undefined local variable or method `string' for main:Object
from (irb):10
from /Users/praveenmody/.rvm/gems/ruby-1.9.3-p448/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
from /Users/praveenmody/.rvm/gems/ruby-1.9.3-p448/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
from /Users/praveenmody/.rvm/gems/ruby-1.9.3-p448/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
Here's my migrate file:
class CreateCoordinates < ActiveRecord::Migration
def change
create_table :coordinates do |t|
t.float :lattitude
t.float :longitude
t.timestamps
end
end
end

Answer 1

Don't run the command in the rails console. Run it from the normal shell within the project directory.

Answer 2

A bit late to answer, hope it helps others :
rails generate migration add_price_to_service_elements price:decimal
followed by:
rails db:migrate
Explanation:
'add' is used to add column, 'price' is the column to be added 'to' references the tablename which is 'service_elements'. If you add up text in quotes seperated by an '_' (underscore) you will get above command. price:decimal further specifies the type of values column would be storing in this case decimal values.
rake db:migrate command checks for latest migration version(maintained in schema_migrations table) and in this case executes the migration version generated by the above command.
As already pointed out such command need to be run from console and within the app directory.
Update : Still to make it work properly, files need to be manually updated for changes to reflect on browser :
for eg. controller, view (index,show,_form) etc.