ALTER TABLE Order_Items
ADD CONSTRAINT Order_Items_Product_ID_FK
FOREIGN KEY (Product_Id)
REFERENCES Product_Information
ON DELETE CASCADE;
为表order_items(Product_id)添加一个外键Order_Items_Product_ID_FK
级联product_Information(product_id),加上ON DELETE CASCADE后，如果主表order_items删除 一条记录，那么product_Information中对应的关联 的数据也跟着删除