How to remove a column from my Rails model?

If you know the columns you want to remove you can use the convention: Remove..From.. when naming your migrations. Additionally you can include the column names when running the migration command.

The form of the command:

rails g migration Remove..From.. col1:type col2:type col3:type

For example:

rails g migration RemoveProjectIDFromProjects project_id:string

generates the following migration file:

class RemoveProjectIdFromProjects < ActiveRecord::Migration
  def self.up
    remove_column :projects, :project_id
  end

  def self.down
    add_column :projects, :project_id, :string
  end
end