EBK DATABASE SYSTEMS: DESIGN, IMPLEMENT
12th Edition
ISBN: 9781305886841
Author: Morris
Publisher: CENGAGE LEARNING - CONSIGNMENT
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Expert Solution & Answer
Chapter 5, Problem 1RQ
Explanation of Solution
Entity Supertype:
- The entity supertype is an entity type that has the relation with one or more subtypes and it contains the common attributes of its subtypes.
- The entity subtype is a grouping of entities type in single entity that shares the common attributes or relationships which are different from other grouping.
Use of entity supertype:
The reason for using entity supertype is to reduce redundant relationships and also reduce the number of nulls.
Example:
The following example demonstrates the “supertype” entity, “subtype” entity, and “discriminator”.
Explanation:
- Here, “Employee” entity is a “supertype” entity.
- “Hourly Employee”, “Salaried Employee”, and “Consultant” are the “Sub type” entities.
- “Emp_type” is a discriminator to select appropriate “subtype”.
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Students have asked these similar questions
Question D.4: FIFO Page Replacement
Consider the following page reference string:
e, c, b, e, a, g, d, c, e, g, d, a
Considering 4 frames, fill in the following table and then answer how many page faults would occur with the
FIFO page replacement algorithm.
RS: reference string; FO: frame 0, F1: frame 1, etc.
Hint: all frames are initially empty, so your first unique pages will all cost one fault each.
Time
1234567891011
12
RS
e
cb
e agd ce g d
a
FO
F1
F2
F3
Page fault?
b) Total # page faults:
c) Briefly (1-2 sentences) explain Belady's Anomaly that can occur in FIFO Page Replacement.
Consider a system that uses a fixed-partition scheme, with equal partitions of size 2" bytes, and the main
memory has 2¹8 bytes. A process table is maintained with a pointer to the resident partition for each resident
process. How many bits are required for the pointer in the process table? Show all your steps.
Use the same semaphore notation shown above to describe how we can ensure the execution order of the
following process execution graph:
P6
P2
P7
P1
P3
P4
P5
Use all of the following semaphores in your answer:
s1=0; s2=0; s3=0; s4=0; s5=0; s6=0;
Chapter 5 Solutions
EBK DATABASE SYSTEMS: DESIGN, IMPLEMENT
Ch. 5 - Prob. 1RQCh. 5 - What kinds of data would you store in an entity...Ch. 5 - Prob. 3RQCh. 5 - What is a subtype discriminator? Give an example...Ch. 5 - Prob. 5RQCh. 5 - What is the difference between partial...Ch. 5 - Prob. 7RQCh. 5 - According to the data model, is it required that...Ch. 5 - Prob. 9RQCh. 5 - Prob. 10RQ
Ch. 5 - Prob. 11RQCh. 5 - Prob. 12RQCh. 5 - Prob. 13RQCh. 5 - When implementing a 1:1 relationship, where should...Ch. 5 - What is time-variant data, and how would you deal...Ch. 5 - Prob. 16RQCh. 5 - Prob. 1PCh. 5 - Prob. 2PCh. 5 - Prob. 3PCh. 5 - Prob. 4PCh. 5 - Prob. 5PCh. 5 - Prob. 6PCh. 5 - Prob. 7PCh. 5 - Prob. 8CCh. 5 - Prob. 9CCh. 5 - Prob. 10C
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