Conceptually, we create an alias I of the table INSTRUCTORS, compute the
product between this alias and INSTRUCTORS and retain those pairs that share
the the same room and consist of distinct individuals.
Example 5.8.3 Suppose that we need to find all triples of student names for
students who live in the same city and state. Now we need to operate with three
distinct copies of the table STUDENTS. This is accomplished by: