I came across a question that states
Consider the following relation schema pertaining to a students
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 minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join ?
I have seen several solutions on Internet like this or this
As per my understanding. maximum tuples should be 8 and minimum should be 8 as well, since for each (rollnum,course) there should be a roll num in Students. Anyone who can help in this regard
If there was a referential constraint in place ensuring that every rollno in Enroll must also appear in Student then your answer of 8 for both minimum and maximum would be correct. The question doesn't actually mention any such constraint however. There's no need to assume that the RI constraint exists just because the rollno attribute appears in both tables. So the best answer is 0 minimum and 8 maximum. If it's a multiple-choice question and 0,8 isn't one of the given answers then answer 8,8 instead - and tell your teacher that the question is unclear.