Assigning custom data types to new columns during migration

The set of data types that you can assign to a new column during a database migration is pretty limited. However, it's easy to set a column to a data type specific to the database that you're using. Instead of specifying :string, :integer, etc for the data type, specify :"data type". As an example, if you have MySQL and you want to add an unsigned integer, there's no way to specify a :integer to be unsigned. But you can do this:

add_column :table, :newcolumn, :"int (10) unsigned"