03 05/2012 1. Consider the relation schemas: faculty (SSN, last-name, first-name
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03 05/2012 1. Consider the relation schemas: faculty (SSN, last-name, first-name, street, city, state) student = (SSN, last-name, first-name, street, city, state) and the following instance: SSNlast-name first-nameetcitystate 388-67-9009 Bai 980-67-8765 JacksonMary 980-67-8765 Robert 435-67-2342 Charles street ShujuPerkinsBaton Rouge LA Tina Courtney Washington Baton Rouge LA Baton Rouge LA Iowa State Baton Rouge LA a. Is this instance a legal instance of relation faculty? Why? b. Is this instance a legal instance of relation student? Why?Explanation / Answer
primary key is a field in instance which can uniquely identifies each rown in a table
a) This instance is a legal instance to relation faculty .
In faculty relation, primary key is last name and in the given instance, each last name is different from others and are unique. So it is a legal instance.
b)This instance is not a legal instance to student relation.
In this student relation, primary key is ssn and in the given instance two tuples are having the same instance i.e 980-67-8765. So it violates the primary key definition and hence this instance is not a valid instance.
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