Consider the following schema:

1. Customer (cust_id, cust_name).
2. Product (prod_code ,prod_name, unit_price)
3. Customer_Order (order_code, order_date, cust_id)
4. Order_Item (order_code, prod_code, num_of_units)

1. Develop DDL of in SQL
2. Add Column contact in Customer Table
3. Add Column company_name in Product Table