A)Write a query to return the listing of customers who did not make purchase during the invoicing period. Sort the results by customer code.

B)Write a query to list the most popular products p_code and p_descript. Products popularity is defined by the total quantity that have already been sold [Hint: you can use view]

C)Write a PL/SQL anonymous block to list those customers full name who has some balance. [Hint: use cursor]

D)Write a PL/SQL anonymous block to calculate the subtotal of an invoice. Initialize a scalar variable to a specified invoice.