Differentiate between degree and cardinality of a relation.

Compared to a file system, how does a database management system avoid redundancy in data through a database?

A school has a rule that each student must participate in a sports activity. So each one should give only one preference for sports activity. Suppose there are five students in a class, each having a unique roll number. The class representative has prepared a list of sports preferences as shown below. Answer the following:

Table: Sports Preferences

1. Roll no 24 may not be interested in sports. Can a NULL value be assigned to that student’s preference field ?
2. Roll no 17 has given two preferences in sports. Which property of relational DBMS is violated here ? Can we use any constraint or key in the relational DBMS to check against such violation, if any?
3. Kabaddi was not chosen by any student. Is it possible to have this tuple in the Sports Preferences relation ?

In another class having 2 sections, the two respective class representatives have prepared 2 separate Sports Preferences tables, as shown below:

Sports preference of section 1 (arranged on roll number column)

Table: Sports Preferences

Sports preference of section 2 (arranged on Sports name column, and column order is also different)

Table: Sports Preferences

Are the states of both the relations equivalent? Justify.