# CS532 Homework 2 ER to Relation Transform

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1. (70%) Transform the provided ER diagram for the Student Registration System to relations
using the techniques discussed in class. For composite attributes, use Method 1 (i.e., use the
more specific attributes only) to perform the transformation.

For each relation obtained,
underscore the key, specify other candidate keys (if any) and foreign keys (if any), and
specify the constraints associated with this relation (including all constraints that are
described in the Requirements Document).

2. (10% for CS532; 20% for CS432) Let A and B be the only attributes of a relation R.
(a) Suppose neither A nor B is a key of R. Does the combination of these two attributes, (A,
B), form a key of R? Why or why not?
(b) Suppose the combination of these two attributes, (A, B), is a key of R. Can either A or B
be a superkey of R? Why or why not?

3. (20% for CS532; 10% for CS432) Consider the following ER Diagram:
Based on the method discussed in Chapter 4 of the Lecture Notes, this 1-to-many relationship
will be transformed into a foreign key attribute in relation Students and null values cannot be
avoided in this attribute.

If you are a CS532 student, propose two different methods to
tackle this problem such that null values can be avoided in the resulted relations/attributes. If
you are a CS432 student, propose just one method to tackle this problem such that null
values can be avoided in the resulted relations/attributes. You can change the ER diagram, if
needed, but the changed ER diagram should be logically equivalent to the original diagram.
(0, 1) (0, m)
Students Courses Is_TA_of