Chapter 3

Question 1

What are the two main activities of the database design process?

Answer 1

1- database design
2- applications design

Question 2

(database design/applications design) focuses on the programs and interfaces that access the database.

Answer 2

application design

Question 3

What does the following diagram represent?

Answer 3

the main phases of database design

Question 4

ER diagrams, EER diagrams, UML Class diagrams, and the use of design tools industry for designing and documenting large scale designs are all methodologies for ____________________.

Answer 4

conceptual design

Question 5

What are the two ways in which a database can be modeled as?

Answer 5

A collection of entites or a relationship among entities

Question 6

An _______ is an object in real world with an independent existence.

Answer 6

entity

Question 7

T/F: The entity can be an object with a physical existence or with a conceptual existence in the real world.

Answer 7

true

Question 8

T/F: Entities have attributes.

Answer 8

true

Question 9

What does the following figure show?

Answer 9

two entities and their attribute values (ex: the entity [e1] and its attribute values [name, address, age, homephone].)

Question 10

________ are properties used to describe an entity.

Answer 10

Attributes

Question 11

T/F: A specific entity will have a value for each of its attributes.

Answer 11

true.

Question 12

T/F: All attributes have the same value set (or data type) associated with it.

Answer 12

false, each one has a value set…

Question 13

T/F: Entity is a basic concept for the ER model.

Answer 13

True

Question 14

_______ are specific things or objects in the mini-world that are represented in the database.

Answer 14

entites

Question 15

What are the 6 types of attributes?

Answer 15

simple, composite, multi-valued, stored, complex and derived.

Question 16

A _______ attribute is when each entity has a single atomic value for the attribute. For example, SSN or Sex.

Answer 16

simple

Question 17

A ________ attribute may be composed of several components.

Answer 17

composite

Question 18

Name 2 composite attributes from the following ER schema diagram.

Answer 18

Address (which is composed of apt#, house#, street, city, state, zipcode, and country.) and Name (which is composed of firstname, middlename, and last name)

Question 19

T/F: Composition may form a hierarchy where some components are themselves composite.

Answer 19

True.

Question 20

A __________ attribute describes an entity which may have multiple values for that attribute. (ex: color of a CAR or PreviousDegrees of a STUDENT. Which will be denoted as _______ or _________)

Answer 20

multi-valued, {Color}, {PreviousDegrees}.

Question 21

A _________ attribute is an attribute value which can be derived from related attributes or entites.

Answer 21

derived

Question 22

Name 2 Derived attributes from the following ER schema diagram.

Answer 22

Age (which can be derived from the birth_date attributes of a person) and Number_of_employees (which can be derived by counting the number of employees related to (working for) that department.)

Question 23

A _______ attribute can have other attributes derived from it.

Answer 23

stored (Ex: Birth_date)

Question 24

T/F: In some cases, two or more attribute values are related.

Answer 24

true, stored and derived attributes are related in which one is derived from the other.

Question 25

A _______ value is used in some cases in which a particular entity may not have an applicable value for an attribute.

Answer 25

null

Question 26

Determine the value of the following:
a College_degrees attribute applies only to people with college degrees.

Answer 26

null value. a person with no college degree would have NULL for College_degrees.

Question 27

______ means not applicable or unknown.

Answer 27

Null (not applicable: dosent exist for some instances and Unknown, not known whether the attribute value exists for some instances. )

Question 28

The two cases in which NULL can be classified under the unknown category are ________ or _________.

Answer 28

missing, or not known.

Question 29

T/F: composite and multi-valued attributes may be nested arbitrarily to any number of levels, although this is rare.

Answer 29

true. they are formed in complex attributes.

Question 30

In a _______ attribute, the composite attribute is between parentheses () and the components are seperated by commas, and the multivalued attributes are displayed between braces {}.

Answer 30

complex. (also called a composite multivalued attribute.)

Question 31

{PreviousDegrees (College, Year, Degree, Field)} is a denoted example of a __________ attribute.

Answer 31

Complex/composite multi-valued attribute

Question 32

Name the subcomponents attributes of: {PreviousDegrees (College, Year, Degree, Field)}

Answer 32

College, Year, Degree, Field.

Question 33

T/F: Multiple {PreviousDegrees (College, Year, Degree, Field)} values cannot exist.

Answer 33

false, multiple values can exist.

Question 34

The following is an example of a ________ attribute.

Answer 34

composite

Question 35

T/F: Attribute names are enclosed in circles and are attached to their entity type by straight lines in ER diagrams.

Answer 35

false, they are enclosed in ovals.

Question 36

T/F: Composite attributes are attached to their component
attributes by straight lines.

Answer 36

true.

Question 37

T/F: composite attributes are displayed in double ovals.

Answer 37

false, multivalued attributes.

Question 38

T/F: Entities with the same basic attributes are grouped or typed
into an entity type.

Answer 38

true.

Question 39

T/F: Each entity type will have a collection of entities stored in the
database.

Answer 39

true

Question 40

Each entity type will have a collection of entities stored in the
database called the _______ or sometimes ________.

Answer 40

entity set, entity collection.

Question 41

T/F: the entity set and the entity type are two seperate concepts that must always have two different names.

Answer 41

false, the entity set is usually referred to using the same name as the entity type. (Ex: EMPLOYEE refers to both a type of entity as well as the current collection of all employee entities in the database.)
However, entity type and entity set may be given
different names.

Question 42

Determine the Entity set and Entity type in the following figure:

Answer 42

Employee and Company are the entity type names.
e1 e2 e3 and c1 c2 are the entity set for each entity type.

Question 43

The following figure shows which state of the entity set?

Answer 43

it shows the current state of the entities of that type that are stored in the database.

Question 44

T/F: Entity set is the current state of the entities of that type
that are stored in the database.

Answer 44

true

Question 45

An attribute of an entity type for which each entity must have a unique value is called a ___________ of the entity type.

Answer 45

key attribute

Question 46

The key attribute is an attribute whose values are _______ for each individual entity in the entity set.

Answer 46

distinct

Question 47

T/F: the key attribute’s values can be used to identify each entity uniquely.

Answer 47

true.

Question 48

T/F: sometimes several attributes together can form a key.

Answer 48

true, the combination of the attribute values must be distinct for each entity.

Question 49

T/F: Every entity must always have a key attribute.

Answer 49

false, an entity type may have no key.

Question 50

An entity type may also have no key, in which case it is called a ______ entity type.

Answer 50

weak

Question 51

T/F: Specifying that an attribute is a key of an entity type means that the preceding uniqueness property must hold for EVERY entity set of the entity type.

Answer 51

True.

Question 52

T/F: The key forms a constraint which prohibits any two entities from having the same value for the key attribute at the same time.

Answer 52

true, It is not the property of a particular entity set; rather, it is a constraint on any entity set of the entity type at any point in time.

Question 53

T/F: A key attribute can never be composite.

Answer 53

false, it may be composite (if possible).

Question 54

T/F: An entity type may have more than one key.

Answer 54

True.

Question 55

T/F: In an ER diagram, each key is underlined.

Answer 55

true.

Question 56

A _________ specifies the set of values associated with an attribute.

Answer 56

value set (domain)

Question 57

T/F: Each simple attribute is associated with a value set.

Answer 57

true.

Question 58

Mathematically, an attribute A for an entity type E whose value set is V is defined as a function..

Answer 58

A(e): E -> P(V)
(Where P(V) indicates a power set (which means all possible subsets) of V. The above definition covers simple and multivalued attributes.)

Question 59

T/F: Value sets are similar to data types in most programming languages – e.g., integer, character (n), real, bit.

Answer 59

true.

Question 60

T/F: In ER diagrams, an entity type is displayed in a square box.

Answer 60

false, rectangular box.

Question 61

T/F: The initial conceptual design of entity types is typically not complete.

Answer 61

true

Question 62

What does the following figure represent in a ER diagram?

Answer 62

it represents a cardinality ratio 1 : N for E1:E2 in R

Question 63

What does the following figure represent in a ER diagram?

Answer 63

a derived attribute

Question 64

What does the following figure represent in a ER diagram?

Answer 64

a weak entity type.

Question 65

What does the following figure represent in a ER diagram?

Answer 65

a structural constraint (min, max) on participation of E in R.

Question 66

What does the following figure represent in a ER diagram?

Answer 66

an indentifying relationship

Question 67

What does the following figure represent in a ER diagram?

Answer 67

Total participation of E2 in R.

Question 68

A __________ relates two or more distinct entities with a specific meaning.

Answer 68

relationship

Question 69

T/F: Relationships of the same type are grouped or typed into a relationship type.

Answer 69

true.

Question 70

The degree of a relationship type is the number of ______________.

Answer 70

participating entity types. (Ex: In COMPANY, Both MANAGES and WORKS_ON are binary relationships.)

Question 71

______ is the schema description of a relationship, and identifies the relationship name and the participating entity types.

Answer 71

Relationship Type.

Question 72

T/F: The relationship type also identifies certain relationship constraints.

Answer 72

true.

Question 73

The current set of relationship instances represented in the database is the ______________.

Answer 73

relationship set.

Question 74

T/F: the relationship set has the current state of the relationship type.

Answer 74

true.

Question 75

T/F: more than one relationship type can exist between the same participating entity types.

Answer 75

true

Question 76

Constraints on Relationship Types are also known as ___________

Answer 76

ratio constraints

Question 77

Cardinality Ratio (specifies ________ participation) while the Existence Dependency Constraint (specifies ________ participation).

Answer 77

maximum, minimum.

Question 78

T/F: the cardinality ratio is also called participation constraint.

Answer 78

false, The existence Dependency Constraint is also called…

Question 79

One-to-one (1:1), One-to-many (1:N) or Many-to-one (N:1), Many-to-many (M:N) are the ___________.

Answer 79

cardinality ratio.

Question 80

In the Existence Dependency Constraint, zero represents _________ participation. Therefore (It is/It is not) existence-dependent.

Answer 80

optional, it is not.

Question 81

In the Existence Dependency Constraint, one or more represents _________ participation. Therefore (It is/It is not) existence-dependent.

Answer 81

mandatory, it is.

Question 82

Determine what is the cardinality ratio for the following figure:

Answer 82

Many-to-Many (M:N)

Question 83

Determine what is the cardinality ratio for the following figure:

Answer 83

Many-to-One (N:1)

Question 84

A relationship type between the same participating entity
type in distinct roles is the ______________ relationship type.

Answer 84

recursive

Question 85

The recursive relationship type is also called a ___________ relationship type.

Answer 85

self-referencing.

Question 86

Determine which relationship type the following figure represents:

Answer 86

the recursive relationship type

Question 87

A weak entity is an entity that does not have a key attribute and that is identification-dependent on __________.

Answer 87

another entity type.

Question 88

A weak entity must participate in an _________ relationship type with an owner or identifying entity type.

Answer 88

identifying.

Question 89

Weak entities are identified by the combination of: a ________ key of the weak entity type, and the particular entity they are related to in the identifying relation type.

Answer 89

partial.

Question 90

T/F: A relationship type can have attributes.

Answer 90

True.

Question 91

T/F: Most relationship attributes are used with M:N relationships.

Answer 91

True.

Question 92

T/F: Relationship attributes in M:N relationships can be transferred to the entity type on the N-side of the relationship.

Answer 92

false, in 1:N relationships…

Question 93

T/F: Total participation constraint (existence dependency) is shown by a ________, and partial participation constraint is by a _________in an ER diagram.

Answer 93

double line, single line.

Question 94

the ___________ constraint specifies that each entity e in E participates in at least min and at most max relationship instances in R.

Answer 94

structural.

Question 95

The default structural contraint is: min=__, max=__.

Answer 95

0,n.
Default(no constraint): min=0, max=n (signifying no limit).

Question 96

T/F: the structural constraint must have min≤max, min≥0, max ≥1.

Answer 96

true.

Question 97

T/F: The structural contraint is specified on each participation of an entity type E in a relationship type R.

Answer 97

true.

Question 98

Determine the structural constraint of the following:
A department has exactly one manager and an employee can
manage at most one department.

Answer 98

Specify (0,1) for participation of EMPLOYEE in MANAGES.
Specify (1,1) for participation of DEPARTMENT in MANAGES

Question 99

Determine the structural constraint of the following:
An employee can work for exactly one department but a
department can have any number of employees.

Answer 99

Specify (1,1) for participation of EMPLOYEE in WORKS_FOR.
Specify (1,n) for participation of DEPARTMENT in WORKS_FOR.

Question 100

Relationship types of degree 2 are called _____.
Relationship types of degree 3 are called _____ and of degree n are called ______.

Answer 100

binary, ternary, n-ary.

Question 101

T/F: In general, an n-ary relationship is not equivalent to n binary relationships.

Answer 101

true.

Question 102

T/F: Constraints are harder to specify for higher-degree relationships (n > 2) than for binary relationships.

Answer 102

true.

Question 103

If a particular binary relationship can be derived from a higher-degree relationship at all times, then it is __________.

Answer 103

redundant.

Question 104

T/F: In some cases, a ternary relationship can be represented as a weak entity.

Answer 104

True, if the data model allows a weak entity type to have multiple identifying relationships (and hence multiple owner entity types)

Question 105

Determine what type of n-ary relationship is represented in the following figure:

Answer 105

a ternary relationship.

Question 106

Determine what type of n-ary relationship is represented in the following figure:

Answer 106

a ternary relationship.

Question 107

Determine what type of n-ary relationship is represented in the following figure:

Answer 107

a redundant ternary relationship.

Question 108

T/F: In higher-degree relationship constraints, the (min, max) constraints can be displayed on the edges – however, they do not fully describe the constraints.

Answer 108

true.

Question 109

In higher-degree relationship constraints, displaying a 1, M, or N indicates ________ constraints. In which, An M or N indicates _________ constraint, and a 1 indicates that an entity can participate in at most _______ relationship instance that has a particular combination of the other participating entities.

Answer 109

additional, no, one.

Question 110

What is needed in general to fully describe the constraints in a higher-degree relationship?

Answer 110

it requires both (min,max) and 1, M, or N to fully describe the constraints.