Multiple choice

Consider the following relation schema pertaining to a students database: Student (rollno, name, address) Enroll (rollno, courseno, coursename) where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and the minimum number of tuples that can be presented in (Student * Enroll), where ' *' denotes natural join?

  1. 8, 8

  2. 120, 8

  3. 960, 8

  4. 960, 120
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C Correct answer
Explanation

Natural join on Student and Enroll (sharing 'rollno'): Max tuples occur if every student is enrolled in all 8 courses (120 * 8 = 960). Min tuples occur if only the students present in Enroll are joined (8).

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