ALTER TABLE purchase_order_items ADD COLUMN expected_delivery_date DATE NULL AFTER quantity;
ALTER TABLE purchase_order_items ADD COLUMN expected_delivery_date DATE NULL AFTER quantity_ordered;
ALTER TABLE purchase_order_items ADD COLUMN actual_delivery_date DATE NULL AFTER expected_delivery_date;
ALTER TABLE purchase_order_items ADD COLUMN qty_received DECIMAL(12,3) NOT NULL DEFAULT 0.000 AFTER actual_delivery_date;
ALTER TABLE purchase_order_items ADD COLUMN delivery_status ENUM('pending','partial','complete','overdue') NOT NULL DEFAULT 'pending' AFTER qty_received",