Altering table

Adding and modifying table with Rails was never so easy and sexy !
You don't need to make tons of add_column for one type.. use change_table !!

and for def self.down use remove_column :table_name, [:column1, :column2 ...]

Add a column

 change_table(:suppliers) do |t|
 t.column :name, :string, :limit => 60
end

Add 2 integer columns

 change_table(:suppliers) do |t|
 t.integer :width, :height, :null => false, :default => 0
end

Add created_at/updated_at columns

 change_table(:suppliers) do |t|
 t.timestamps
end

Add a foreign key column

 change_table(:suppliers) do |t|
 t.references :company
end

Creates a company_id(integer) column

Add a polymorphic foreign key column

 change_table(:suppliers) do |t|
 t.belongs_to :company, :polymorphic => true
end

Creates company_type(varchar) and company_id(integer) columns

Remove a column

 change_table(:suppliers) do |t|
 t.remove :company
end

Remove several columns

 change_table(:suppliers) do |t|
 t.remove :company_id
 t.remove :width, :height
end

Remove an index

 change_table(:suppliers) do |t|
 t.remove_index :company_id
end

HAVE FUN !!