CS 186
MIDTERM
FALL 1994
There are 9 questions to this exam. All count equally.
Queries expressed in relational algebra and relational calculus must follow
the syntax used in class. Queries expreseed in SQL must follow the syntax
used in class or in the INGRES Manual. All SQL queries should contain NO
duplicates in their outputs. It is not necessary to sort the outputs in any
order.
You are not allowed to use views for any questions expect question 7.
Use the following relational database schema for all the questions except
question 1:
DEPT (dname, location)
STUDENT (name, regno, gpa, level, dept)
COURSE (cno, cname, dept)
TAKE (regno, cno)
None of the columns can have null values.
Problem #1
Suppose there are two relations A (a1, a2, a3) and B (b1, b2, b3). A has two candidate keys and its primary
key is (a1, a2). B has only one candidate key and its primary key is (b2, b3). How many candidate keys will
the relation A times B have? How many primary keys will the relation A times B have? Please state your
reasoning in support of your conclusion.
Problem #2
Express in relational algebra the names of the EECS students who are taking any EECS courses.
Problem #3
Express in relational calculus the names of the departments which either have no students or have at least one
student taking each EECS course.
CS 186, MIDTERM, FALL 1994
CS 186MIDTERMFALL 1994professor (e.g., Professor J. Wawrzynek) 1
