Suppose you run a Web site that includes a banner<br /><br />advertise
+ment service. You contract with companies<br /><br />that want their 
+ads displayed when poeple visit<br /><br />the pages on your site. Ea
+ch time a visitor hits<br /><br />one of your pages, you serve an ad 
+embedded in the<br /><br />page that is sent to the visitor's browser
+ and<br /><br />assess the company a small fee. To represent this<br 
+/><br />information, you maintain three tables. One table,<br /><br /
+>company, has columns for company name, number,<br /><br />address, a
+nd telephone number. Another table, ad<br /><br />lists ad numbers, t
+he number for the company that<br /><br />owns the ad, and the amount
+ you charge per hit.<br /><br />The third table, hit, logs each ad hi
+t by number<br /><br />and the date on which the ad was<br /><br />se
+rved.
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