http://blog.csdn.net/li_001/article/details/53857336

增加表
rails g model water_temperature position:integer name:string en_name:string

删除新增错误的表
rails d model water_temperature position:integer name:string en_name:string

新增表字段
rails g migration add_column_water_temperature_id_into_product
def up
add_column :products, :water_temperature_id, :integer
end
def down
remove_column :water_temperature_id
end

删除表字段
rails g migration remove_column_water_temperature_id_into_product
def change
remove_column :skus, :face_price_id
end

修改字段
rails g migration rename_column_seat_powers_id_into_product
def up
rename_column :products, :seat_powers_id, :seat_power_id
end

def down
rename_column :products, :seat_power_id, :seat_powers_id
end

修改字段属性
rails g migration change_column_seat_powers_into_product
def up
change_column :products, :seat_powers, :string
end

def down
change_column :products, :seat_powers, :integer
end