# a1ans - Model Answers to Assignment 1 For these exercises,...

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Model Answers to Assignment 1 For these exercises, I recommend that you write a sequence of assignment statements of the form R := . . . with Answer as the last variable assigned a value. Just be sure that it is unambiguous what the attributes of each computed relation are. (Use the renaming operation when necessary to make the attributes clear.) Each exercise is worth 10 points (30 points total). CISC 437 students 1. Exercise 2.4.1, parts a, b, c, d, e. Model answer (a) R := σ speed ≥ 3.00 (PC) Answer := π model (R) model 1005 1006 1013 (b) R := σ hd ≥ 100 (Laptop) S := Product | X | R Symbol | X | means natural join Answer := π maker (S) maker E A B F G (c) R := σ maker = B (Product | X | PC) S := σ maker = B (Product | X | Laptop) T := σ maker = B (Product | X | Printer) U := π model, price (R)

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V := π model, price (S) W := π model, price (T) Answer := U U V U W model price 1004 649 1005 630 1006 1049 2007 1429 (d) R := σ color = true AND type = lazer (Printer) Answer := π
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## This note was uploaded on 11/03/2009 for the course CISC 437 taught by Professor Schwartz,l during the Fall '08 term at University of Delaware.

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a1ans - Model Answers to Assignment 1 For these exercises,...

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