It looks like you don't have an "id" - not "item_type_id" - just plain
old "id" column. Rails works best if tables have "id" as their.
It's recommended you use migrations to build and mange your database
tables - this will automatically create the "id" column for you
(amongst other things).
I think if you change the name of your primary key column to "id"
however I think you'll move forward...