Consider the following ER diagram. Assume that an employee may work in up to two departments or may not be assigned to any department. Assume that each department must have one and may have up to three phone numbers. Assume the following additional system requirements: Each department can have anywhere between 1 and 30 employees. Each phone is used by one, and only one, department. Each phone is assigned to at least one and may be assigned to up to 30 employees. ● ● • Each employee is assigned at least one, but no more than 5 phones. a) Supply (min, max) constraints on this diagram. State clearly any additional assumptions you make. b) Under what conditions would the relationship HAS PHONE been redundant in this example? EMPLOYEE C ) J HAS PHONE ( , ) WORKS IN PHONE (,) ) DEPARTMENT (,) CONTAINS

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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Consider the following ER diagram. Assume that an employee may work in up to two
departments or may not be assigned to any department. Assume that each department must have
one and may have up to three phone numbers.
Assume the following additional system requirements:
Each department can have anywhere between 1 and 30 employees.
Each phone is used by one, and only one, department.
Each phone is assigned to at least one and may be assigned to up to 30 employees.
●
●
●
• Each employee is assigned at least one, but no more than 5 phones.
a) Supply (min, max) constraints on this diagram. State clearly any additional assumptions you
make.
b) Under what conditions would the relationship HAS PHONE been redundant in this example?
EMPLOYEE
C )
J
HAS PHONE
(.
)
WORKS IN
PHONE
(
)
DEPARTMENT
(,)
CONTAINS
Transcribed Image Text:Consider the following ER diagram. Assume that an employee may work in up to two departments or may not be assigned to any department. Assume that each department must have one and may have up to three phone numbers. Assume the following additional system requirements: Each department can have anywhere between 1 and 30 employees. Each phone is used by one, and only one, department. Each phone is assigned to at least one and may be assigned to up to 30 employees. ● ● ● • Each employee is assigned at least one, but no more than 5 phones. a) Supply (min, max) constraints on this diagram. State clearly any additional assumptions you make. b) Under what conditions would the relationship HAS PHONE been redundant in this example? EMPLOYEE C ) J HAS PHONE (. ) WORKS IN PHONE ( ) DEPARTMENT (,) CONTAINS
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