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HW2 Solution

# HW2 Solution - Database Management Systems(CIS 4301(Spring...

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Database Management Systems (CIS 4301) (Spring 2008) Instructor: Dr. Markus Schneider TAs: Ganesh Viswanathan Wenjie Yuan Homework 2 Solution Name: UFID: Email Address: Pledge (Must be signed according to UF Honor Code) On my honor, I have neither given nor received unauthorized aid in doing this assignment. _______________________________________________Signature For scoring use only: Maximum Received 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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