Database Management Systems (CIS 4301)
(Spring 2008)
Instructor: Dr. Markus Schneider
TAs:
Ganesh Viswanathan
Wenjie Yuan
Homework 2 Solution
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Exercise 1
15
Exercise 2
15
Exercise 3
10
Exercise 4
30
Exercise 5
30
Total
100
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Exercise 1 (Knowledge Questions) [15 points]
Answer the following questions. [3x5=15pts]
1. What are multivalued attributes?
Multivalued attributes are those which can have many values. For example, a person
can have many phone numbers etc.
2. What are the differences between Natural Join and Theta Join?
Natural Join is based on all the equal domains of two relations, it is associative and
commutative.
Theta Join is based on the join condition F.
3. What are aggregate functions? Give examples of some aggregate functions
available as an extension of Relational Algebra.
Aggregate Functions are functions that take a set of values and that yield a single
value in a result tuple. Examples: sum, avg, count, min, max for sum, average,
number, minimum, maximum, of a multiset (bag) of values (not contained in the
relational model).
4. What is generalization?
“
Factoring
”
(extracting) properties (attributes, relationships) of similar entity
subclass, subtypes, categories) to a common superclass (supertype).
5. What is a 1 : m relationship set R between two entity sets E1 and E2?
Each member of E1 can be associated with any number of members from E2.
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 Spring '08
 Schneider
 Databases, Sid

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