Assuming that you generate 15,000 invoices per month, what recommendation would you give the designer about the use of derived attributes?

 Assuming that you follow the recommendations you gave in Problem 29, how would you rewrite the query?

 What indexes would you recommend for the query you wrote in Problem 30, and what SQL commands would you use?

 How would you rewrite the query to ensure that the index you created in Problem 31 is used?