Let R = (A, B, C), and let r1 and r2 both be relations on schema R.

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Let R = (A, B, C), and let r1 and r2 both be relations on schema R. Give an expression in SQL that is equivalent to each of the following queries.

a. r1 ∪ r2

b. r1 ∩ r2

c. r1 − r2

d. II AB(r1) 1 ΠBC(r2)

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Database System Concepts

ISBN: 978-0072554816

4th Edition

Authors: Henry F. Korth, S. Sudarshan

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Question Posted: Jan 28, 2011 05:54 AM

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Let R = (A, B, C), and let r1 and r2 both be relations on schema R.

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a r1 r2 select from r1 union select from r2 b r1 r2 we can write this using the in...View the full answer

Database System Concepts

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