lec07.366

lec07.366 - . . Winter 2008 CPE/CSC 366: Database Modeling,...

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Unformatted text preview: . . Winter 2008 CPE/CSC 366: Database Modeling, Design and Implementation Alexander Dekhtyar . . Functional Dependencies in Databases Examples Functional Dependencies Example 1: Functional Dependencies Consider the following relation Purchases : Purchases(ReceiptNo,Ordinal, PDate, Customer, Item, Price) Each tuple of the relation stores information about a single item purchased by a customer. The information stored is the receipt number, the position of the item on the receipt (item scanned first has Ordinal = 1 , next item Ordinal = 2 , etc.), the date of the purchase, the name of the customer, the name of the purchased item and its price. Consider the following fragment of the Purchases table. ReceiptNo Ordinal PDate Customer Item Price 1234 1 01/21/2008 "Fausto Klosner" "Chocolate Chip Cookie" 0.95 1234 2 01/21/2008 "Fausto Klosner" "Rye Bread" 2.50 3042 1 01/23/2008 "Susie Gladney" "Rye Bread" 2.50 3042 2 01/23/2008 "Susie Gladney" "Opera Cake" 15.00 3403 1 01/26/2008 "Susie Gladney" "Ganache Cookie" 1.30 5612 1 01/26/2008 "Dean Dews" "Chocolate Chip Cookie" 0.95 We can make the following statements about the Purchases relation: 1. Receipt number uniquely identifies the customer.1....
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lec07.366 - . . Winter 2008 CPE/CSC 366: Database Modeling,...

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