It is easily possible to remove a column using rails migration.
class SomeClass < ActiveRecord::Migration
def self.up
remove_column :table_name, :column
You can run the codes in up method directly in rails console:
>> ActiveRecord::Migration.remove_column :table_name, :column_name
If you already have a migration file such as "db/migrate/20130418125100_remove_foo.rb", you can do this:
>> require "db/migrate/20130418125100_remove_foo.rb"
>> RemoveFoo.up
If you just want to do rake db:migrate, try this:
>> ActiveRecord::Migrator.migrate "db/migrate"