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DBMS Korth Edition 6 Exercise 3 Question 24 (Page No. 111)
Consider the query: with dept total (dept name, value) as (select dept name, sum(salary) from instructor group by dept name), dept total avg(value) as (select avg(value) from dept total) select dept name from dept total, dept total avg where dept total.value >= dept total avg.value; Rewrite this query without using the with construct.

ajaysoni1924 asked in Databases Mar 30, 2019

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DBMS Korth Edition 6 Exercise 3 Question 23 (Page No. 111)
Consider the query: select course id, semester, year, sec id, avg (tot cred) from takes natural join student where year = 2009 group by course id, semester, year, sec id having count (ID) >= 2; Explain why joining section as well in the from clause would not change the result.

ajaysoni1924 asked in Databases Mar 30, 2019

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DBMS Korth Edition 6 Exercise 3 Question 22 (Page No. 110)
Rewrite the where clause where unique (select title from course) without using the unique construct.

ajaysoni1924 asked in Databases Mar 30, 2019

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DBMS Korth Edition 6 Exercise 6 Question 17 (Page No. 254)
Let R = (A, B) and S = (A, C), and let r (R) and s(S) be relations. Write SQL Queries equivalent to the following domain relational- calculus expressions: a. {< a > | $\exists b (< a, b > \epsilon¸r \wedge b$ = 17)} b. ... ))}

ajaysoni1924 asked in Databases Mar 30, 2019

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DBMS Korth Edition 6 Exercise 7 Question 25 (Page No. 321)
Consider the relation schemas are shown below, which were generated from the E-R diagram in Figure given below. For each schema, specify what foreign key constraints, if any, should be created. teaches (ID, course id, sec id, semester, ... room number) inst dept (ID, dept name) stud dept (ID, dept name) course dept (course id, dept name)

ajaysoni1924 asked in Databases Mar 30, 2019

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DBMS Korth Edition 6 Exercise 7 Question 29 (Page No. 321)
Explain the distinction between total and partial constraints.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 28 (Page No. 321)
Explain the distinction between disjoint and overlapping constraints.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 27 (Page No. 321)
Explain the distinction between condition-defined and user-defined constraints. Which of these constraints can the system check automatically? Explain your answer.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 26 (Page No. 321)
Design a generalization-specialization hierarchy for a motor vehicle sales company. The company sells motorcycles, passenger cars, vans, and buses. Justify your placement of attributes at each level of the hierarchy. Explain why they should not be placed at a higher or lower level.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 23 (Page No. 320)
Design a database for an airline. The database must keep track of customers and their reservations, flights and their status, seat assignments on individual flights, and the schedule and routing of future flights. Your design ... , a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 22 (Page No. 319-320)
Design a database for a worldwide package delivery company (e.g., DHL or FedEx). The database must be able to keep track of customers (who ship items) and customers (who receive items); some customers may do both. ... E-R diagram, a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 21 (Page No. 319)
Design a database for an automobile company to provide to its dealers to assist them in maintaining customer records and dealer inventory and to assist sales staff in ordering cars. Each vehicle is identified by a vehicle ... , a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 20 (Page No. 319-320)
Consider the E-R diagram in Figure given below, which models an online bookstore. a. List the entity sets and their primary keys. b. Suppose the bookstore adds Blu-ray discs and downloadable videos to its collection. ... model the case where a shopping basket may contain any combination of books, Blu-ray discs, or downloadable video.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 19 (Page No. 319)
We can convert any weak entity set to a strong entity set by simply adding appropriate attributes. Why, then, do we have weak entity sets?

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 18 (Page No. 319)
Explain the difference between a weak and a strong entity set.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 15 (Page No. 319)
Construct an E-R diagram for a hospital with a set of patients and a set of medical doctors. Associate with each patient a log of the various tests and examinations conducted.

ajaysoni1924 asked in Databases Mar 28, 2019

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17

DBMS Korth Edition 6 Exercise 7 Question 14 (Page No. 318)
Explain the distinctions among the terms primary key, candidate key, and superkey.

ajaysoni1924 asked in Databases Mar 28, 2019

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18

DBMS Korth Edition 6 Exercise 7 Question 13 (Page No. 318)
Temporal changes: An E-R diagram usually models the state of an enterprise at a point in time. Suppose we wish to track temporal changes, that is, changes to data over time. For example, Zhang may have been a student between ... , with the above extensions to track temporal changes. b. Convert the above E-R diagram into a set of relations.

ajaysoni1924 asked in Databases Mar 28, 2019

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19

DBMS Korth Edition 6 Exercise 7 Question 12 (Page No. 317-318)
Figure shows a lattice structure of generalization and specialization (attributes not shown). For entity sets A, B, and C, explain how attributes are inherited from the higher-level entity sets X and Y. Discuss how to handle a case where an attribute of X has the same name as some attribute of Y.

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 11 (Page No. 317)
In SQL, foreign key constraints can only reference the primary key attributes of the referenced relation, or other attributes declared to be a super key using the unique constraint. As a result, total participation constraints on a ... 4.4.7 of korth). (Unfortunately, these features are not supported on any widely used database currently.)

ajaysoni1924 asked in Databases Mar 28, 2019

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21

DBMS Korth Edition 6 Exercise 7 Question 10 (Page No. 317)
Consider a many-to-one relationship R between entity sets A and B. Suppose the relation created from R is combined with the relation created from A. In SQL, attributes participating in a foreign key constraint can be null. Explain how a constraint on total participation of A in R can be enforced using not null constraints in SQL.

ajaysoni1924 asked in Databases Mar 28, 2019

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22

DBMS Korth Edition 6 Exercise 7 Question 9 (Page No. 317)
Suppose the advisor relationship was one-to-one. What extra constraints are required on the relation advisor to ensure that the one-to-one cardinality constraint is enforced?

ajaysoni1924 asked in Databases Mar 28, 2019

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DBMS Korth Edition 6 Exercise 7 Question 8 (Page No. 317)
Consider a relation such as sec_course, generated from a many-to-one relationship sec_course. Do the primary and foreign key constraints created on the relation enforce the many-to-one cardinality constraint? Explain why.

ajaysoni1924 asked in Databases Mar 28, 2019

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24

DBMS Korth Edition 6 Exercise 7 Question 6 (Page No. 316-317)
Consider the representation of a ternary relationship using binary relationships as described in this book and illustrated in Figure (b) (attributes not shown) a. Show a simple instance of E, A, B,C, RA, RB, and RC that cannot correspond ... for E. Show how to treat E as a weak entity set so that a primary-key attribute is not required.

ajaysoni1924 asked in Databases Mar 28, 2019

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25

DBMS Korth Edition 6 Exercise 7 Question 5 (Page No. 316)
An E-R diagram can be viewed as a graph. What do the following mean in terms of the structure of an enterprise schema? a. The graph is disconnected. b. The graph has a cycle.

ajaysoni1924 asked in Databases Mar 28, 2019

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26

DBMS Korth Edition 6 Exercise 7 Question 4 (Page No. 316)
Consider an E-R diagram in which the same entity set appears several times, with its attributes repeated in more than one occurrence. Why is allowing this redundancy a bad practice that one should avoid?

ajaysoni1924 asked in Databases Mar 28, 2019

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27

DBMS Korth Edition 6 Exercise 7 Question 3,17 (Page No. 316-319)
Design an E-R diagram for keeping track of the exploits of your favorite sports team. You should store the matches played, the scores in each match, the players in each match, and individual player statistics for each match. ... . b)Extend the E-R diagram of above exercise to track the same information for all teams in a league.

ajaysoni1924 asked in Databases Mar 28, 2019

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28

DBMS Korth Edition 6 Exercise 7 Question 2 (Page No. 315)
Consider a database used to record the marks that students get in different exams of different course offerings (sections). a. Construct an E-R diagram that models exams as entities, and uses a ternary relationship, for the ... a particular student and section pair, yet you can represent the marks that a student gets in different exams.

ajaysoni1924 asked in Databases Mar 28, 2019

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29

DBMS Korth Edition 6 Exercise 7 Question 1 (Page No. 316)
Construct an E-R diagram for a car insurance company whose customers own one or more cars each. Each car has associated with it zero to any number of recorded accidents. Each insurance policy covers one or more cars and has one ... is for a particular period of time and has an associated due date, and the date when the payment was received.

ajaysoni1924 asked in Databases Mar 28, 2019

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30

DBMS Korth Edition 6 Exercise 6 Question 18 (Page No. 254)
Let R = (A, B) and S = (A, C), and let r (R) and s(S) be relations. Using the special constant null, write tuple-relational-calculus expressions equivalent to each of the following: a. r $ROJ$ s b. r $FOJ$ s c. r $LOJ$ s

ajaysoni1924 asked in Databases Mar 27, 2019

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