How do you run migrations forward?

How do you create a new migration?

What should the self.down method do in a migration?

What Rails data type should you use to represent currency values?

How do you add a new field to a record?

With the rake db:migrate command (or db:migrate in the Rake window on Heroku).

To keep in line with Rails’ timestamp-based naming convention, it’s best to use script/generate migration NameOfMigration, and then edit the resulting file in the db/migrate directory.

The self.down method defines what should happen if the migration is rolled back using rake db:rollback. The tables, column, and indexes created in self.up need a corresponding removal process in self.down.

The :decimal type is the most precise way to keep track of money. It can keep track of cents to the right of the decimal point and will contain values with a fixed number of decimal places much more accurately than :float.

New fields get created with add_column, as “fields” are represented as columns and the records that contain them as rows.