Ms$.$ Marcia Wilson owns and operates Marcia$$s Dry Cleaning, which is an upscale dry clean$-$er in a well$-$to$-$do suburban neighborhood. Marcia makes her business stand out from the competition by providing superior customer service. She wants to keep track of each of her customers and their orders. Ultimately, she wants to notify them that their clothes are ready via email and$/$or text.

Assume that Marcia has hired you as a database consultant to develop an operational database having the following four tables:

CUSTOMER $($CustomerID$,$ FirstName, LastName, Phone, EmailAddress$)$ INVOICE $($InvoiceNumber $,$ CustomerID $,$ DateIn, DateOut, Subtotal, Tax, TotalAmount$)$ INVOICE$\_$ITEM $($ InvoiceNumber $,$ ItemNumber, ServiceID $,$ Quantity, UnitPrice, ExtendedPrice$)$

SERVICE $($ServiceID$,$ ServiceDescription, UnitPrice$)$

A$.$ Assume that Marcia$$s has the following personnel: two owners, a shift manager, a part$-$time seamstress, and two salesclerks. Prepare a two$-$to three$-$page memo that ad$-$dresses the following points: $1.$ The need for database administration. $2.$ Your recommendation as to who should serve as database administrator. Assume that Marcia$$s is not sufficiently large to need or afford a full$-$time database administrator.

$3.$ Using the main topics in this chapter as a guide, describe the nature of database administration activities at Marcia$$s$.$ As an aggressive consultant, keep in mind that you can recommend yourself for performing some of the DBA functions.

B$.$ For the employees described in part A$,$ define users, groups, and permissions on data in these four tables. Use the security scheme shown in Figure $6-21$ as an example. Create a table like that in Figure $6-23.$ Don$$t forget to include yourself.

C$.$ Suppose that you are writing a part of an application to create new records in SERVICE for new services that Marcia$$s will perform. Suppose that you know that while your procedure is running, another part of the same application that records new or modifies existing customer orders and order line items can also be running. Additionally, suppose that a third part of the application that records new customer data also can be running. $1.$ Give an example of a dirty read, a nonrepeatable read, and a phantom read among this group of applications.

$2.$ What concurrency control measures are appropriate for the part of the application that you are creating?

$3.$ What concurrency control measures are appropriate for the two other parts of the application?

D$.$ Suppose a frequent query at Marcia$$s Dry Cleaning is to request information about all invoices that came in on the previous day. Marcia and her employees have noticed that this query appears to be running very slowly. What is one thing you can do$,$ as DBA, to improve the response time of this query?