Item_Inv

Add "sublot_no" (string40, nullable) before "grade_cd" to store the sublot of the item stored here.

Change "grade_cd" and "status_cd" from non-nullable to nullable so these fields of the lot or sublot tables will be usable as defaults.

Add inhibit-delete foreign key from "item_id" and "lot_no" to lot, and from "item_id" , "lot_no", and "sublot_no" to sublot.

Add inhibit-delete foreign keys from "grade_cd" to item_grade, and from "status_cd" to item_state.