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Databases Flashcards

Study for CP2404 final exam

1
Q

attribute

A

A characteristic of an entity or object. An attribute has a name and data type.

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2
Q

binary relationship

A

An ER term for an association (relationship) between two entities. For example PROFESSOR teaches COURSE.

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3
Q

business rule

A

A description of a policy, procedure or principle within an organisation. For example, a pilot cannot be on duty for more than 10 hours during a 24-hour period, or a professor may teach up to four classes during a semester.

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4
Q

candidate key

A

A minimal superkey; that is, a key that does not contain a subset of attributes that is itself a superkey.

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5
Q

cardinality

A

A property that assigns a specific value to connectivity and expresses the range of allowed entity occurrences associated with a single occurrence of the related entity.

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6
Q

class diagram notation

A

The set of symbols used in the creation of class diagrams.

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7
Q

closure

A

A property of relational operators that permits the use of relational algebra operators on existing tables (relations) to produce new relations.

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8
Q

completeness constraint

A

A constraint that specifies whether each entity supertype occurrence must also be a member of at least one subtype. The completeness constraint can be partial or total. Partial completeness means that some supertype occurrences might not be members of nay subtype. Total completeness means that every supertype occurrence must be a member of at least one subtype.

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9
Q

composite attribute

A

An attribute that can be further subdivided to yield additional attributes. For example, a phone number such a 6158982368 may be divided into an area code (615), an exchange number (898), and a four digit code (2368). Compare to simple attribute

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10
Q

composite entity

A

An entity designed to transform an M:N relationship to two 1:M relationships. The composite entity’s primary key comprises at least the primary keys of the entities that it connects. Also known as bridge entity. See also linking table.

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11
Q

composite identifier

A

In ER modeling, a key composed of more than one attribute.

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12
Q

composite key

A

A multiple attribute key.

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13
Q

conceptual model

A

The output of the conceptual design process. The conceptual model provides a global view of an entire database and describes the main data objects, avoiding details

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14
Q

conceptual schema

A

A representation of the conceptual model, usually expressed graphically.

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15
Q

connectivity

A

The classification of the relationship between entities. Classifications include 1:1, 1:M, and M:N.

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16
Q

constraint

A

A restriction placed on data usually the form of rules. For example, “A student’s GPA must be between 0.00 and 4.00.” Constraints are important because they help to ensure data integrity.

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17
Q

crow’s foot notation

A

A representation of the entity relationship diagram that uses a three-pronged symbol to represent te “many” sides of the relationship.

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18
Q

data dictionary

A

A DBMS component that stores metadata–data about data. Thus, the data dictionary contains the data definition as well as their characteristics and relationships. A data dictionary may also include data that are external to the DBMS. Also know as an information resource dictionary.

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19
Q

data redundancy

A

A condition in which the data environment contains redundant (unnecessarily duplicated) data.

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20
Q

database system

A

An organisation of components that defines and regulates the collection, storage, management, and use of data in a database environment.

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21
Q

dependent

A

An attribute whose value is determined by another attribute.

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22
Q

derived attribute

A

An attribute that does not physically exist within the entity and is derived via an algorithm. For example, the Age attribute might be derived by subtracting the birth date from the current date.

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23
Q

design trap

A

A problem that occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world. The fan trap is the most common design trap.

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24
Q

determinant

A

Any attribute in a specific row whose value directly determines other values in that row.

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25
Q

determination

A

The role of a key. In the context of a database table the statement “A determines B” indicates that knowing the value of attribute A means that the value of attribute B can be looked up.

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26
Q

difference

A

Difference is a relational set operator that yields all rows in one table that are not found in the other table; that is, it subtracts one table from the other table which eliminates duplicates. Tables must be union compatible.

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27
Q

disjoint subtype

A

In a specialisation hierarchy, a unique and nonoverlapping subtype entity set.

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28
Q

Domain

A

In data modelling to construct used organise and describe an attribute’s set of possible values

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29
Q

Entity

A

person place thing concept or events for which data can be stored

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30
Q

Entity Cluster

A

a virtual entity type used to represent multiple entities and relationships in the ERD. An entity cluster is formed by combining multiple interrelated entities into a simple single abstract entity object. An entity cluster is considered virtual abstract because it is not really an entity in the final ERD.

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31
Q

Entity instance

A

in ER modelling a specific table row also known as an entity occurrence.

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32
Q

entity integrity

A

the property of a relational table that guarantees each entity has unique value in primary key and that the key has no null values.

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33
Q

entity relationship diagram

A

A diagram that depicts an entity relationship model’s entities, attributes, and relations.

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34
Q

entity subtype

A

in a generalisation specialisation hierarchy a subset of an entity super-type the entity super-type contains the common characteristics and the subtypes contained the unique characteristics of each entity

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35
Q

entity supertype

A

in a generalisation specialisation hierarchy a generic entity chance it contains the common characteristics of entity sometimes.

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36
Q

existence dependent

A

A property of an entity his existence depends on when I’m on the entities in such an environment the existence of independent table must be created and loaded first because the existence dependent he cannot reference the table that does not yet exist.

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37
Q

existence independent

A

A property of an entity that can exist apart from one or more related entities. Such a table must be created first one referencing in an existence dependent table.

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38
Q

external model

A

the application program is view of the data environment. Given its business focus, and external model works with the data subset of the global database schema.

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39
Q

external schema

A

the specific representation of an external view; the end users you of the daughter environment.

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40
Q

Fan trap

A

A design error that occurs when one entity is in one to many relationships with other entities that produces an association among the other entities that is not expressed in the model.

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41
Q

Foreign key

A

That should be like to be in one table Israelis much my last match the primary key in another table or he says must be now

42
Q

Full functional dependence

A

A condition in which actually dysfunctionally dependent on a composite key but not on any subset

43
Q

Functional dependence

A

With in relation are and actually be functionally dependent on actually a if and only if the given value of actually a determined exactly one day about you beingThe relationship quite B is depending on a unquote is equivalent toQuite a determine the unquote and is written as baby

44
Q

Generalisation

A

In a specialisation hierarchy the grouping of common actually into a super type entity

45
Q

Hardware Independence

A

Condition in which a model does not depend on hardly used in the models implementation therefore changes in the hardware will have no effect on the database design conceptualLevel

46
Q

Hierarchical model

A

An early database model is basic concepts and characteristics formed the basis of subsequent database development. This model is based on upside down tree structure in which each record is called the segmentWill stopTop record is the root segment each segment has a one to many relationship to segment directly below it.

47
Q

Identifiers

A

In an ER and unique name to be gently instant. In the relational model, such identifiers are up to primary keys and tables.

48
Q

Inheritance

A

Any object oriented garden model, the ability of an object to inherit the dey destruction and methods of classes are bothered in the class hierarchy.

49
Q

Internal model

A

In database modelling, I level of the abstraction that DAT conceptual model to a specific DBMS model to implementation.Internal model is the representation of the database as clay scene” by the DBMS. In other words, the internal model requires a designer to match the conceptual models characteristics and constraints today to the selected implementation model.

50
Q

Internal schema

A

A representation of an internal model using database contract constructs supported by the chosen database.

51
Q

key

A

An entity identify a based on the concept of functional dependents; please maybe classified in several ways. Examples include super keys candidate keys firing key secondary keys phone keysForeign please

52
Q

Key attributes

A

That attributes that form the primary key

53
Q

Logical design

A

I stay in a stage in the design phase that matches the conceptual design to the requirements of the selected DBMS it is therefore software independentLogical design and used to translate the conceptual design into the internal model for a selected database management systemThat is DVT SQL Server Oracle IMs Informix access for ingress

54
Q

Logical independence

A

A condition in which the internal model can be changed without affecting the conceptual model.(The internal model is hardly independent because it is unaffected by the computer on which the software installed. Therefore, changing storage devices operating systems, in fact affects the internal model.)

55
Q

Mandatory participation

A

Relationship England in which one and two parents must have a corresponding parenting another entity for example, an employee works in a division,(a person can’t be an employee without being signed to a company’s division.)

56
Q

M:N

A

Association among Kilmartin to which one of parents of an empty is associated with many occurrences ever related entity and one parents of the related entities associated with many occurrences of the firstAnd 13

57
Q

Multi-valued attribute

A

And actually that can have many values for a single entity parents for example thenAnd degree actually it might store the string BBA MBA PhD to indicate three different degrees hell

58
Q

Natural key (natural identifier)

A

They generally accepted identifies the real world Objects. As its name implies, financial keys familiar to end users and forms partly day-to-day business vocabulary.

59
Q

Network model

A

I don’t model standards created in the late 1960s the represented dad is a collection of record types and relationships predefined sex with an own record type and a member record type in a one to many relationship

60
Q

1:M

A

Associations among two more interviews that are used by Donna models in a one to many relationship finding to the incentive associated with many instances of the related

61
Q

1:1

A

Associations 12 or more interviews that are used by data models in a one to one relationship one entity incident is associated with only one instance of the related entity

62
Q

Optional attribute

A

In the ER modelling and actually that does not require a value; therefore, it can be left empty.

63
Q

Optional participation

A

In ER modelling, a condition in which wanted to your parents does not require a corresponding entity occurrence in particular relationship.

64
Q

Overlapping subtype

A

In a specialisation hierarchy, a condition in which each entity instance or road of the super tight canopy in more than one subtype.

65
Q

Partial completeness

A

In a generalisation hierarchy, a condition in which some super-type occurrences might not be members of any subtype.

66
Q

Participants

A

And ER term to entities that participate in a relationship for example in the relationship professor teachers class teachers relationship is based on the participant professor and class

67
Q

Physical model

A

A model in which physical characteristics such as vacation, path, and format described for the data. The physical model is both hardware and software dependent

68
Q

Primary key

A

In the relational model, and identify a composed of one on my Chevy is that uniquely identifies a row. Also, I can make key selected as a new unique entity identifier.

69
Q

Recursive relationship

A

Relationship found within A single entity type. For example, an employee is married to an employee for our part is a component of another part.

70
Q

Referential integrity

A

A condition by Richard depend on tables foreign key must have either no entry or a matching entry in a related table. Even though anchovies may not have a corresponding actually it is impossible to have an invalid entry.

71
Q

Regular entity

A

An entity that is existent independent that is it can exist apart from all of its related entities. Also called a strong entity

72
Q

Relation

A

In a relational database model, an entity set. Relations are implemented as tables relations are related to each other through the sharing of common entity characteristic(Everywhen:).

73
Q

Relational diagram

A

A graphical representation of a relational databases entities actually to them then entities and relationships among the entities.

74
Q

Relational model

A

Developed by ES kind of IBM in 1970 it represents a major breakthrough thing uses and designers because of its conceptual simplicityRelational model is based on mathematical set theory and represents dad is independent relations each relation(table) is conceptually represented as a matrix of intersecting rows and columns. The relations are related to each other through the sharing of common entity characteristics(values and columns).

75
Q

Relational schema

A

The organisation of a relational database as described by the database administrator.

76
Q

Relationship

A

An association among entities

77
Q

Relationship degree

A

The number of entities or participants associated with the relationship. A relationship degree can be you merry by Mary turn aerial higher

78
Q

Relvar

A

Short for relation variable, a variable that holds the relation. Rollbar is a container(variable) the holding relation dad are not the relation itself

79
Q

Required attributes

A

In ER modelling, I naturally that must have a value. In other words, it cannot be left empty.

80
Q

Schema

A

A magical grouping of database objects, such as tables, indexes, views, and queries, that I related to each other.Usually, as email belongs to a single user or application.

81
Q

Secondary key

A

A key you strictly forgot a retrieval purposes. For example, customers are not likely to know the customer number(primary key), but the combination of theirLast name, first name, middle initial, and telephone number will probably match the appropriate table rate.

82
Q

Segments

A

In the hierarchical got a model, the equivalent of a filesystems record type.

83
Q

Simple attribute

A

Attributes that cannot be further subdivided into meaningful components.

84
Q

Single-valued attributes

A

Attributes that have only one value

85
Q

Software independence

A

A property of any model application that does not depend on the software used to be implemented.

86
Q

Specialisation

A

In a specialisation hierarchy, the grouping of unique attributes into a subtype entity.

87
Q

Specialisation hierarchy

A

A hierarchy based on the top down process of identifying lower level, more specific entity subtypes from a higher level entity super-type. Specialisation is based on grouping unique characteristics and relationships of the subtypes.

88
Q

Strong relationship

A

A relationship that occurs when two entities are existence-dependent; from a database design perspective, this relationship exists whenever the primary key of the related entity contains the primary key in the parent entity.

89
Q

Subschema

A

In the network model, proportion of the database “seen” by the application programs that produce the desired information from the data in the database.

90
Q

Subtype

A

An entity that contains unique characteristics (attributes) in a more broadly defined entity known as the super-type. In a generalisation hierarchy a subtype is an entity below a parent entity. For example pilot could be some type of the super-type employee.

91
Q

Subtype discriminator

A

An attribute in the super-type entity that determines to which entity subtype each super-type occurrence is related.

92
Q

Super key

A

An attribute or attributes that uniquely identify each entity in a table.

93
Q

Surrogate key

A

A system assigned primary key generally numeric and auto-incremented.

94
Q

System catalogue

A

A detailed system data dictionary that describes all objects in a database

95
Q

Table

A

A matrix composed of intersecting rows (entities) and columns (attributes) that represents an entity set in the relational model.

96
Q

Ternary relationship

A

An ER term used to describe an association (relationship) between three entities

97
Q

Time variant data

A

Data whose values are a function of times.

98
Q

tuple

A

In the relational model, a table row.

99
Q

Unary relationship

A

An ER term used to describe an association with in an entity. For example, a course might be a prerequisite to another course.

100
Q

Unique index

A

An index in which the index key can have only one associated pointer value (row).

101
Q

Weak entity

A

An entity that displays existence dependence and inherits the primary key of its parent entity. For example a dependent requires the existence of an employee.

102
Q

Weak relationship

A

a relationship in which the primary key of the related entity does not contain a primary key component of the parent entity.

Databases (3 decks)

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