Once you change the database scheme, you need to increment the version in your SQLiteOpenHelper implementation. Doing that, next time you app launches you can handle the database change in the
onUpgrade(SQLiteDatabase db,int old Version,int newVerison)
There you can do anything you like..alter table, drop table etc..
or.. you can simply uninstall you app. It will delete the database.
There is a good tutorial on this here: http://www.vogella.com/tutorials/AndroidSQLite/article.html
ps: sorry it was upgrade not update.