Midterm

Data anomolies

Abnormalities when all changes in redundant data are not made correctly update insert delete

Internal model

DBMS view dependent on software logical independence- changes won't affect the conceptual model

Data dependence

Data access changes when storage characteristics change

Data independence

Data storage changes don't affect data access

Database system

Defines and regulates the 1. collection 2. storage 3. management 4. use of data

Physical model

Disk view Lowest level of abstraction relational model aimed at logical model physical independence- changes won't affect the internal model

Conceptual model

Global view combines all external views ERD independent of hardware and software

External Model

Highest degree of abstraction End user's view of the data

Referential integrity

If the FK contains a value, that value refers to an existing valid row in another relation

DBMS

Manages structure and controls access to data manages interaction between end user and the database

Controlled redundancy

Redundancies okay if they make the relationship work

Data redundancy

Same data stores unnecessarily in different places

Structural independence

You can change the file structure without affecting data access

A CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of ____ integrity. A) entity B) null C) referential D) complete

a

A verb associating two nouns in a business rule translates to a(n) ____ in the data model. A) relationship B) constraint C) attribute D) entity

a

A(n) ____ database is designed to support a company's day-to-day operations. A) transactional B) workgroup C) desktop D) enterprise

a

A(n) ____ is a restriction placed on the data. A) constraint B) relationship C) entity D) attribute

a

Another name for a composite entity is a ____ entity. A) bridge B) linked C) directive D) referring

a

In a database context, a(n) ____ indicates the use of different names to describe the same attribute. A) synonym B) homonym C) entity D) duplicate

a

Students and classes have a ____ relationship. A) many-to-many B) one-to-one C) one-to-many D) many-to-one

a

Which of the following is an example of structured data? A) A spreadsheet B) An e-mail C) A Web page D) A memo

a

____ data exist in a format that does not lend itself to processing that yields information. A) Unstructured B) Semistructured C) Structured D) Historical

a

____ exists when different versions of the same data appear in different places. A) Data inconsistency B) Improved decision making C) Better data integration D) Data consistency

a

____ provide(s) a description of the data characteristics and the set of relationships that link the data found within the database. A) Metadata B) Queries C) Information D) End-user data

a

PK

a candidate key selected to uniquely identify all other attribute values in any given row

Candidate key

a superkey without unnecessary attributes

Structural dependence

access is DEPENDENT on its own structure

FK

an attribute whose values match primary key values in the related table

key attribute

any attribute that is part of a key

Superkey

any key that uniquely identifies each row

Entity

anything that can have data collected about it

A ____ is any key that uniquely identifies each row. A) special B) superkey C) selective D) candidate

b

A workgroup database is a(n)____ database. A) distributed B) multiuser C) enterprise D) single-user

b

No data entry at all is known as a(n) ____. A) empty B) null C) zero D) nil

b

Referential ____ means that if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation. A) direction B) integrity C) relations D) uniqueness

b

A ____ is a logically connected set of one or more fields that describes a person, place, or thing. A) database B) column C) record D) file

c

The ____ data model uses the concept of inheritance. A) network B) entity relationship C) object-oriented D) relational

c

many-to-many

cannot be implemented in any relational model can be changed into one-to-many using a bridge or composite entity

field

character(s) that describe a specific characteristic

Attribute

characteristic of an entity

file

collection of related records

Composite key

composed of more than one attribute

Data inconsistency

conflicting versions of the same data occur in different places

A noun in a business rule translates to a(n) ____ in the data model. A) attribute B) relationship C) constraint D) entity

d

All primary key entries are unique, and no part of a primary key may be ____. A) zero B) a candidate key C) a foreign key D) null

d

The ____ model is the end users' view of the data environment. A) abstract B) conceptual C) internal D) external

d

Advantages of DBMS

data sharing data security integration access decision making productivity

System catalog

describes objects contains metadata

Data dictionary

describes tables contains all attribute names and characteristics for each table in the system contains metadata

Entity integrity

each row in the table has its own unique identity Table has a primary key. Primary key column has no null entries and are unique

existence independence

entity can exist apart from one or more related entities

existence dependence

entity exists only when it is associated with another related entity occurrence

Two conditions weak entities meet

existence dependent pk partially or totally derived from parent entity in relationship

Problems with File system data processing

extensive programming o ad hoc queries system administration is difficult difficult to make changes to existing structures bad security

Well designed database

facilitates data management generates accurate and valuable info

5 parts of a database system

hardware software people procedures data

Physical data format

how a computer works with data

Logical data format

how a human views the data

one-to-many

ideal

Data maintenance operations

inserting new records deleting new records updating existing records

Secondary key

key strictly used for data retrieval purposes

Info is the bedrock of

knowledge

record

logically connected set of one or more fields that a person, place, event, or thing

Nulls

no data entry not permitted in pk, represents: unknown missing N/A

OO model

objects that share similar characteristics are grouped in classes classes are organized in a class hierarchy Inheritance

Optional participation

one entity occurrence does not require corresponding entity occurrence in particular relationship

Mandatory participation

one entity occurrence requires corresponding entity occurrence in particular relationship

one-to-one

rare could mean entity components were not defined properly could indicate that two entities belong in the same table

Data,

raw facts, building blocks of info

Constraint

restriction placed on the data

Info

result of processing raw data to reveal meaning

Synonym

same attribute, different names

Homonym

same name, different attributes

Database

shared, integrated computer structure that stores a collection of end user data and metadata

Each program must contain

specification of file type Record specification field definitions

Business rules

standardize company's view of the data

DBMS functions

stores definitions of data elements and relationships in the dictionary looks up required data component structures and relationships provides data abstraction and removes dependencies

Operational

transaction or production

Multiuser databases

workgroup enterprise