マイグレーション

class CreatePublications < ActiveRecord::Migration
def change
create_table :publications do |t|
t.string :title
t.text :description
t.references :publication_type
t.integer :publisher_id
t.string :publisher_type
t.boolean :single_issue

t.timestamps
end
add_index :publications, :publication_type_id
end
end

bin/rails db:migrate
bin/rails db:rollback

create_table(table_name,options)
drop_table(table_name)
add_column(table_name,column_name,type,options)
change_column(table_name,colum_name,type,options)
remove_column(table_name,*column_names)
add_index(table_name,*column_names)
remove_index(table_name,index_name)
既存のテーブル
追加　add_column
変更 change_column

entriesテーブル

published_on
def changeadd_column :entries, :published_on :date
end