If you have two different tables than you would have two different
classes (models) to work with. Let say that you have two classes
OldThing and NewThing. You want to copy all of the records from the
old_things table to the new_things table. You would do it like this:
old_things = OldThing.find(:all, :conditions => my_sql_where_clause)
old_things.each do |old_thing|
This would go through each of the records in the old_things table and
add them to the new_things table assuming the field names matched up.