foreign-keys

I want to change the datatype of some primary-key columns in my database from INT to BIGINT. The following definition is a toy-example to illustrate the problem: CREATE TABLE IF NOT EXISTS `owner` ( `id` int(11) NOT NULL AUTO_INCREMENT, `thing_id` int(11) NOT NULL, PRIMARY KEY (`id`), KEY `thing_id` (`thing_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ; DROP TABLE IF EXISTS `thing`; CREATE TABLE IF NOT EXISTS `thing` ( `id` int(11) NOT NULL AUTO_INCREMENT, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;

What algorithms are known to perform the task of updating a database by inserting, updating, and deleting rows in the presence of database constraints? More specifically, say that before images of rows to be deleted, after images of rows to be inserted, and both images of rows to be updated are in memory. The rows might be for several tables. An exact sequence of updates is either not known or has not been preserved -- only the before images and the after images that the database must ultimately be made to reflect are known. The database contains primary key, foreign key, and unique index

I am working on an app that will manage students enrolled in a course. The app will have users who can log in and manipulate students. Users can also comment on students. So three of our main classes are Student, User, and Comment. The problem is that I need to associate individual comments with both of the other models: User and Student. So I've started with some basic code like this... class Student < ActiveRecord::Base has_many :comments end class User < ActiveRecord::Base has_many :comments end class Comment < ActiveRecord::Base belongs_to :student belongs_to :user attr_accessible :comment