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IS230 > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

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

A

1- database design
2- applications design

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2
Q

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

A

application design

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3
Q

What does the following diagram represent?

A

the main phases of database design

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4
Q

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 ____________________.

A

conceptual design

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5
Q

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

A

A collection of entites or a relationship among entities

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6
Q

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

A

entity

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7
Q

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

A

true

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8
Q

T/F: Entities have attributes.

A

true

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9
Q

What does the following figure show?

A

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

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10
Q

________ are properties used to describe an entity.

A

Attributes

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11
Q

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

A

true.

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12
Q

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

A

false, each one has a value set…

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13
Q

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

A

True

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14
Q

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

A

entites

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15
Q

What are the 6 types of attributes?

A

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

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16
Q

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

A

simple

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17
Q

A ________ attribute may be composed of several components.

A

composite

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18
Q

Name 2 composite attributes from the following ER schema diagram.

A

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

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19
Q

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

A

True.

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20
Q

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 _________)

A

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

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21
Q

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

A

derived

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22
Q

Name 2 Derived attributes from the following ER schema diagram.

A

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.)

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23
Q

A _______ attribute can have other attributes derived from it.

A

stored (Ex: Birth_date)

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24
Q

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

A

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

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25
Q

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

A

null

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26
Q

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

A

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

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27
Q

______ means not applicable or unknown.

A

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

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28
Q

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

A

missing, or not known.

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29
Q

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

A

true. they are formed in complex attributes.

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30
Q

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

A

complex. (also called a composite multivalued attribute.)

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31
Q

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

A

Complex/composite multi-valued attribute

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32
Q

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

A

College, Year, Degree, Field.

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33
Q

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

A

false, multiple values can exist.

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34
Q

The following is an example of a ________ attribute.

A

composite

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35
Q

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

A

false, they are enclosed in ovals.

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36
Q

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

A

true.

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37
Q

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

A

false, multivalued attributes.

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38
Q

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

A

true.

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39
Q

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

A

true

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40
Q

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

A

entity set, entity collection.

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41
Q

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

A

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.

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42
Q

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

A

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

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43
Q

The following figure shows which state of the entity set?

A

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

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44
Q

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

A

true

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45
Q

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

A

key attribute

46
Q

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

A

distinct

47
Q

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

A

true.

48
Q

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

A

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

49
Q

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

A

false, an entity type may have no key.

50
Q

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

A

weak

51
Q

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.

A

True.

52
Q

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.

A

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.

53
Q

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

A

false, it may be composite (if possible).

54
Q

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

A

True.

55
Q

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

A

true.

56
Q

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

A

value set (domain)

57
Q

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

A

true.

58
Q

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

A

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.)

59
Q

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

A

true.

60
Q

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

A

false, rectangular box.

61
Q

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

A

true

62
Q

What does the following figure represent in a ER diagram?

A

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

63
Q

What does the following figure represent in a ER diagram?

A

a derived attribute

64
Q

What does the following figure represent in a ER diagram?

A

a weak entity type.

65
Q

What does the following figure represent in a ER diagram?

A

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

66
Q

What does the following figure represent in a ER diagram?

A

an indentifying relationship

67
Q

What does the following figure represent in a ER diagram?

A

Total participation of E2 in R.

68
Q

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

A

relationship

69
Q

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

A

true.

70
Q

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

A

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

71
Q

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

A

Relationship Type.

72
Q

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

A

true.

73
Q

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

A

relationship set.

74
Q

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

A

true.

75
Q

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

A

true

76
Q

Constraints on Relationship Types are also known as ___________

A

ratio constraints

77
Q

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

A

maximum, minimum.

78
Q

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

A

false, The existence Dependency Constraint is also called…

79
Q

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

A

cardinality ratio.

80
Q

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

A

optional, it is not.

81
Q

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

A

mandatory, it is.

82
Q

Determine what is the cardinality ratio for the following figure:

A

Many-to-Many (M:N)

83
Q

Determine what is the cardinality ratio for the following figure:

A

Many-to-One (N:1)

84
Q

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

A

recursive

85
Q

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

A

self-referencing.

86
Q

Determine which relationship type the following figure represents:

A

the recursive relationship type

87
Q

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

A

another entity type.

88
Q

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

A

identifying.

89
Q

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.

A

partial.

90
Q

T/F: A relationship type can have attributes.

A

True.

91
Q

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

A

True.

92
Q

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

A

false, in 1:N relationships…

93
Q

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

A

double line, single line.

94
Q

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

A

structural.

95
Q

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

A

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

96
Q

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

A

true.

97
Q

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

A

true.

98
Q

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

A

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

99
Q

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

A

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

100
Q

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

A

binary, ternary, n-ary.

101
Q

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

A

true.

102
Q

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

A

true.

103
Q

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

A

redundant.

104
Q

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

A

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

105
Q

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

A

a ternary relationship.

106
Q

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

A

a ternary relationship.

107
Q

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

A

a redundant ternary relationship.

108
Q

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.

A

true.

109
Q

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.

A

additional, no, one.

110
Q

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

A

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

IS230 (13 decks)

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