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database midterm Flashcards

1
Q

Data

A

Raw Info

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2
Q

Field

A

Group of info with meaning

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3
Q

Record

A

One or more fields connected

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4
Q

File

A

Collection of related records

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5
Q

Data Redundancy

A

Same data is stored unnecessarily at different places

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6
Q

Data Independence

A

Data access is unaffected by changes in the physical data storage

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7
Q

Database Management System (DBMS)

A

A collection of programs that manages the database

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8
Q

Main Components of a Database System

A

Hardware, Software, Data, People, Procedures

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9
Q

Metadata

A

Data about data

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10
Q

Common Problems of Spreadsheets

A
  • Lengthy Development Times
  • Difficulty getting quick answers
  • Complex system admin
  • Lack of security and data sharing
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11
Q

Importance of Data Modelling

A

Creates a sound data structure that real-world operations can depend on

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12
Q

Business Rule

A

A brief and precise description of a policy or procedure within an organization

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13
Q

Features of the Relational Data Model

A
  • Used with Query Language and RDBMS

- Lower data redundancy

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14
Q

Entity Relational Data Model (ERDM)

A

A simple, graphic database structure model for people to interpret

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15
Q

Three Types of Relationships

A
  • 1 to 1; 1:1
  • 1 to Many; 1:M
  • Many to Many: M:N
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16
Q

Table

A

A 2-D structure composed of intersecting rows and columns

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17
Q

Big Data Phenomenon

A

A movement to find new and better ways to manage large amounts of data while providing high performance and scalability at a reasonable cost

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18
Q

3 V’s

A

Volume: amount of data sored
Velocity: speeds at which data grows and processed to get info
Variety: data can be collected in different data format

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19
Q

Sparse Data

A

Data with nulls or empty files

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20
Q

Logical Independence

A

Changing the internal model without affecting the model

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21
Q

Physical Independence

A

Physical model can be changed without affecting the internal model

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22
Q

Entity Integrity

A

Each row in a table has its own unique identity primary key

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23
Q

Referential Integrity

A

Every reference to an entity instance by another entity instance is valid

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24
Q

Requirements to be Union-Compatible

A

Both relations must have the same amount of attributes and the corresponding columns must share the same domain

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25
Q

Natural Join

A

Link tables by selecting only rows with common values in their common attribute

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26
Q

Equijoin

A

Links tables on the basis of an equality condition that compares specified columns of each table

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27
Q

Outer Join

A

Matched pairs are retained. Any unmatched values in the other table would be left null

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28
Q

Avoid Homonyms and Synonyms

A

Homonyms use the same name as the attributes

Synonyms indicate the sue of a different name to describe the same attribute

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29
Q

Two Conditions Met to be Classified as a Weak Entity

A
  • Entity must show the existence dependence

- Entity must intake the primary key of its parent entity

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30
Q

Cardinality

A

Minimal and maximum number of an entity. Useful for setting limits.

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31
Q

Derived Attributes

A

An attribute calculated from existing values

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32
Q

Existence Dependence

A

An entity can only exist when associated with another entity

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33
Q

Relationship Degree

A

Specifies the number of different and unique entities associated with a relationship in a database

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34
Q

Binary Relationship

A

Two entity association

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35
Q

Unary Relationship

A

Associated with its own single entity

36
Q

Ternary Relationship

A

Three entity association

37
Q

Composite Attribute

A

Attributes that can be subdivided to provide additional information and new attributes

38
Q

Simple Attributes

A

Attributes that can not be subdivided

39
Q

Weak Relationship

A

Foreign key is not a primary key

40
Q

Strong Relationship

A

Related entity has a primary key component of parent key

41
Q

Primary Key

A

An important key that uniquely identifies a row

a table can have only one primary key

42
Q

Candidate Key

A

Multiple keys that can act as primary key

a table can have multiple candidate keys

43
Q

Alternate Key

A

Candidate keys other than a primary key

44
Q

Super Key

A

Candidate keys added to the primary key

45
Q

Composite Key

A

A key that consists of more than one attribute to uniquely identify rows in a table

46
Q

Foreign Key

A

A column of a table which points to the primary key of another table. Act as a cross reference between tables

47
Q

Recursive Relationship

A

A relationship between two entities that are similar entity sets of occurrences

48
Q

Normalization

A

Process of assigning attributes to entities to reduce data anomalies by eliminating data redundancies

49
Q

1NF

A

Table must contain no multivalued attributes

50
Q

2NF

A

Contain no partial dependencies

51
Q

3NF

A

Contain no transitive dependencies

52
Q

Partial Dependency

A

Attribute that is part of the primary key that can determine another attribute

53
Q

Three Data Anomalies

A

Data structures that can Update, Insert, or Delete

54
Q

Transitive Dependency

A

Two non-key attributes are dependencies and one of the keys is partially dependent to the primary key

55
Q

Surrogate Key

A

Is an identifier that uniquely identifies an entity in a database that does not thrive on obtaining data. Used to connect different tables together

56
Q

Denormalization

A

Combines tables together to improve the performance of data at a cost of more data redundancy

57
Q

Flags

A

Special code to indicate the absence of value

58
Q

Relvar

A

Variable that holds a relation

59
Q

Inner Join

A

Only returns matched records from the tables that are being joined

60
Q

Theta Join

A

Links tables using an inequality comparison operator

61
Q

Select

A

Unary operator that yields a horizontal subset of a table

62
Q

Project

A

Unary operator that yields a vertical subset of a table

63
Q

Union

A

Combines all rows from two tables, excluding duplicate rows, must be union-compatible

64
Q

Intersect

A

Yields only the rows that appear in both tables, must be union-compatible

65
Q

Difference

A

Yields all rows in one table that are not found in the other table, must be union-compatible

66
Q

Product

A

Yields all possible pairs of rows from two tables

67
Q

Divide

A

Uses one double-column table as the dividend and one single-column table as the divisor.
Output is a single column that contains all values from the second column of the dividend that is associated with every row in the divisor.

68
Q

Data Dictionary

A

Description of all tables in the database created by the user and designer

69
Q

System Catalog

A

System data dictionary that describes all objects within the database

70
Q

Index Key

A

Index’s reference point that leads to data location identified by the key

71
Q

Unique Index

A

Index key can have only one pointer value associated with it

72
Q

NoSQL

Advantages and Disadvantages

A

Advantages

  • High scalability, availability
  • Low-cost hardware
  • Supports Big Data
  • Improves storage efficiency

Disadvantages

  • Complex programming
  • No relationship support
  • No transaction integrity support
73
Q

Object-Oriented Model

Advantages and Disadvantages

A

Advantages

  • Semantic content is added
  • Visual representation
  • Inheritance promotes data integrity

Disadvantages

  • Slow development of standards
  • Complex navigational system
  • Learning curve is steep
74
Q

Entity Relationship Model

Advantages and Disadvantages

A

Advantages

  • Visual modeling yields conceptual simplicity
  • Visual representation makes it an effective communication tool
  • Integrated with the dominant relational model

Disadvantages

  • Limited constraint representation
  • Limited relationship representation
  • No data manipulation language
  • Loss of info content occurs with attributes are removed from entities
75
Q

Relational Model

Advantages and Disadvantages

A

Advantages

  • Structural independence is promoted using independent tables
  • Tabular view improves the simplicity
  • Ad hoc query capability
  • Isolates the end-user from physical-level details

Disadvantages

  • Requires substantial hardware and system software
  • May promote information problems
76
Q

Network Model

Advantages and Disadvantages

A

Advantages

  • Conceptual simplicity
  • Handles more relationship types
  • Data access is flexible
  • Includes data definition language and data manipulation language

Disadvantages

  • System complexity limits efficiency
  • Navigational system yields complex implementation
  • Structural changes require changes in all application programs
77
Q

Hierarchical Model

A

Advantages

  • Promotes data sharing
  • Parent/child relationship promotes conceptual simplicity
  • Database security
  • Efficient with 1:M relationships

Disadvantages

  • Requires knowledge of physical data storage characteristics
  • Navigational system requires knowledge of the hierarchical path
  • No data definition
  • Changes in the structure requires changes in all application programs
78
Q

Extended Relational Data Model (ERDM)

A

Supports OO features, extensible data types based on classes, and inheritance

79
Q

Extensible Markup Language (XML)

A

Manages unstructured data for efficient and effective exchange of data

80
Q

Unified Modeling Language (UML)

A

Describes sets of diagrams and symbols to graphically model a system

81
Q

Class

A

Collection of similar objects with shared structure and behaviour organized in a class hierarchy

82
Q

Class Hierarchy

A

Resembles an upside-down tree in which each class has only one parent

83
Q

Inheritance

A

Object inherits methods and attributes of classes above it

84
Q

4NF

A

No independent multivalued dependencies

85
Q

Delete Anomaly

A

When you delete an entity which can unintentionally delete other entities which you don’t want

86
Q

Business Rule

A

Serve communication tool between the users and designers

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