migration isn't changing my database

This may a common problem, but I created a migration to change a table
that already had some information in it. The rows that were already in
the tables didn't add the additional column. Would I need to drop all
the information in my table and add it back, because that would be
kind of a pain to do...

No I don't believe so. v
I had my table with some rows of data. I created a new migration that
added an additional column to the table, but the column isn't showing
up when I did a "rake db:migrate"