4. Write a SELECT statement that returns the InvoiceNumber and balance due for every invoice with a non-zero balance and an InvoiceDueDate thats less than 30 days from today.

7. Add a column to the query described in exercise 4 that uses the RANK() function to return a column named BalanceRank that ranks the balance due in descending order.

InvoiceTotal - PaymentTotal = Balance

Table Name : Invoices

Table Colums: InvoiceID, VendorID, InvoiceNumber, InvoiceDate, InvoiceTotal, CreditTotal, InvoiceDueDate,PaymentDate