The problems for this chapter use a database for a simple department store that sells items to customers and wants to keep track of the invoices, the selling price $($if an item is on sale$),$ and the sales tax $(7\%)$ to be collected on some items. Every customer and invoice are assigned unique numbers. All items have a Universal Product Code $($UPC$)$ number and bar$-$code assigned to each unique item. Food and non$-$carbonated beverages are not taxed, but clothing, home goods, and most other items are.

The structure of the tables is described in the following crows foot ERD: