1) Let r be a relation instance with schema R = (A, B, C, D). We define...
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1) Let r be a relation instance with schema R = (A, B, C, D). We define r1 = ‘select A,B,C from r’ and r2 = ‘select A, D from r’. Let s = r1 * r2 where * denotes natural join. Given that the decomposition of r into r1 and r2 is lossy, which one of the following is TRUE? (a) s is subset of r (b) r U s = r (c) r is a subset of s (d) r * s = s Answer (c) Consider the following example with lossy decomposition of r into r1 and r2. We can see that r is a subset of s.
Related Book For
Practical Management Science
ISBN: 978-1305250901
5th edition
Authors: Wayne L. Winston, Christian Albright
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