migrating with loosing data

rubyonrails-talk
1

I have already created a migration. It adds 5 columns. Now I edit migration file and enter 2 more column.

How can I remigrate so that 2 new columns would be added without loosing data with db:migrate:reset?

2

By putting it in a new migration file instead of adding it to an already deployed one.

script/generate migration AddTwoMoreColumns

and then in the migration (assuming you are using Rails 2.1):

class AddTimeZoneToUser < ActiveRecord::Migration`
`  def self.up`
`    change_table :users do |t|`
`      t.string :time_zone`
`      t.belongs_to :role`
`    end`
`  end`
``
`  def self.down`
`    change_table :users do |t|`
`      t.remove :time_zone`
`      t.remove_belongs_to :role`
`    end    `
`  end`
`end

(example taken from: http://www.akitaonrails.com/2008/5/25/rolling-with-rails-2-1-the-first-full-tutorial-part-1))

Time to go pick up a book and start reading about how to use Rails. The Rails Way would be a good start.

Best regards

Peter De Berdt