How to solve “Cannot add a NOT NULL column with default value NULL” in SQLite3?

Question

I am getting the following error while trying to add a NOT NULL column to an existing table. Why is it happening ?. I tried rake db:reset thinking that the existing records

Answer 1

If you have a table with existing rows then you will need to update the existing rows before adding your null constraint. The Guide on migrations recommends using a local model, like so:

Rails 4 and up:

class AddDivisionIdToProfile < ActiveRecord::Migration
  class Profile < ActiveRecord::Base
  end

  def change
    add_column :profiles, :division_id, :integer

    Profile.reset_column_information
    reversible do |dir|
      dir.up { Profile.update_all division_id: Division.first.id }
    end

    change_column :profiles, :division_id, :integer, :null => false
  end

end

Rails 3

class AddDivisionIdToProfile < ActiveRecord::Migration
  class Profile < ActiveRecord::Base
  end

  def change
    add_column :profiles, :division_id, :integer

    Profile.reset_column_information
    Profile.all.each do |profile|
      profile.update_attributes!(:division_id => Division.first.id)
    end

    change_column :profiles, :division_id, :integer, :null => false
  end

end