Technology ReviewTechnology Review

Professor MartinProfessor MartinProfessor XiongProfessor Xiong

CSUSCSUS

This lecture is based primarily on Romney & This lecture is based primarily on Romney & Steinbart(2003). It also draws on Martin (2002).Steinbart(2003). It also draws on Martin (2002).

Updated on: Monday, January 27, 2003Updated on: Monday, January 27, 2003

AgendaAgenda Database Management–An IntroductionDatabase Management–An Introduction Relational DatabaseRelational Database Entity-Relationship DiagramEntity-Relationship Diagram

WHAT IS DATA MANAGEMENT?WHAT IS DATA MANAGEMENT?(The first seven slides are based on Watson (2002))(The first seven slides are based on Watson (2002))

The management of The management of organizational memoryorganizational memory Involves designing, using, and managing Involves designing, using, and managing

memory systems of modern organizationsmemory systems of modern organizations

EXAMPLES OF INDIVIDUAL AND EXAMPLES OF INDIVIDUAL AND ORGANIZATIONAL MEMORY SYSTEMSORGANIZATIONAL MEMORY SYSTEMS

INDIVIDUALINDIVIDUAL Internal memoryInternal memory External memory (diaries, bookmarks, address External memory (diaries, bookmarks, address

books)books) ORGANIZATIONAL ORGANIZATIONAL

examples people, filing cabinets, policy examples people, filing cabinets, policy manuals, planning boards, and computers. (Do manuals, planning boards, and computers. (Do organizations have external memories?)organizations have external memories?)

Characteristics similar to Individual memoryCharacteristics similar to Individual memory

DESIRABLE ATTRIBUTES OF DESIRABLE ATTRIBUTES OF ORGANIZATIONAL MEMORYORGANIZATIONAL MEMORY

ShareableShareable readily accessed by more than one person at a timereadily accessed by more than one person at a time

TransportableTransportable Easily moved to a decision makerEasily moved to a decision maker

SecureSecure Protected from destruction and unauthorized useProtected from destruction and unauthorized use

AccurateAccurate Reliable, precise recordsReliable, precise records

TimelyTimely Current and up-to-dateCurrent and up-to-date

RelevantRelevant Appropriate to the decisionAppropriate to the decision

TYPICAL PROBLEMS WITH FILE-TYPICAL PROBLEMS WITH FILE-BASED SYSTEMSBASED SYSTEMS

Organizational memoryOrganizational memory may be seen as a may be seen as a vast, vast, disorganized data warehouse. disorganized data warehouse. Problems include:Problems include:

Redundancy:Redundancy: same data stored in different memories same data stored in different memories Data control:Data control: data not managed as a valuable resource data not managed as a valuable resource Interface:Interface: difficult to access data difficult to access data Delays:Delays: long delays in responding to requests for data long delays in responding to requests for data Lack of reality:Lack of reality: data do not reflect the complexity of the data do not reflect the complexity of the

real worldreal world Lack of data integration:Lack of data integration: data dispersed across different data dispersed across different

systems; also where data is stored may not be known.systems; also where data is stored may not be known.

File-Oriented ApproachFile-Oriented Approach

Applicationprogram #2

Applicationprogram #1

File # 1

Item A Item B Item C

File # 2

Item B Item D Item E

DATABASE APPROACH TO DATABASE APPROACH TO MANAGING PERSISTENT DATAMANAGING PERSISTENT DATA

The database approach emphasizes the The database approach emphasizes the integration and sharing of data across integration and sharing of data across the organization. the organization.

Database ApproachDatabase Approach

Applicationprogram #3

Applicationprogram #2

Databasemanagement

system

Applicationprogram #1

Item A Item B Item C Item D Item E

Database

BENEFITS OF BENEFITS OF THE DATABASE APPROACHTHE DATABASE APPROACH

Redundancy can be reducedRedundancy can be reduced Thus, inconsistency can be avoidedThus, inconsistency can be avoided Integration of dataIntegration of data Data can be shared among applicationsData can be shared among applications Standards can be enforced by the DBAStandards can be enforced by the DBA

formats, representation, naming, formats, representation, naming, documentationdocumentation

Security restrictions can be applied Security restrictions can be applied

BENEFITS OF BENEFITS OF THE DATABASE APPROACHTHE DATABASE APPROACH

Data integrity can be maintainedData integrity can be maintained by minimizing inconsistencyby minimizing inconsistency by having controls to check against incorrect by having controls to check against incorrect

updates, especially in the multi-user contextupdates, especially in the multi-user context

BENEFITS OF BENEFITS OF THE DATABASE APPROACHTHE DATABASE APPROACH

Data independenceData independence Broadly -- the immunity of applications to change in storage Broadly -- the immunity of applications to change in storage

structure and access techniquestructure and access technique Logical -- capacity to change conceptual schema without Logical -- capacity to change conceptual schema without

changing application programs (e.g., adding an attribute or an changing application programs (e.g., adding an attribute or an entity type)entity type)

Physical -- capacity to change internal schema without having to Physical -- capacity to change internal schema without having to change external or conceptual schema (e.g., creating additional change external or conceptual schema (e.g., creating additional access structures to improve retrieval performance)access structures to improve retrieval performance)

Ease of Application Development Ease of Application Development Data accessibility and responsiveness enhancedData accessibility and responsiveness enhanced Reduced program maintenanceReduced program maintenance

SOME DEFINITIONSSOME DEFINITIONS What is a database?What is a database?

a a shared collectionshared collection of of logically related logically related persistent datapersistent data, designed to meet the needs of , designed to meet the needs of multiple usersmultiple users usually within an organization. usually within an organization.

What is a database management system?What is a database management system? DBMS is a collection of programs that enables DBMS is a collection of programs that enables

users to define, construct and manipulate a users to define, construct and manipulate a database. (More detailed defn. later). database. (More detailed defn. later).

What is a database system?What is a database system?

FUNCTIONS OF A DBMSFUNCTIONS OF A DBMS Data definition using DDLData definition using DDL Data manipulation using DMLData manipulation using DML Data security and integrityData security and integrity Data recovery and concurrency controlData recovery and concurrency control Data dictionaryData dictionary Satisfactory performanceSatisfactory performance

STEPS IN DATABASE STEPS IN DATABASE DEVELOPMENT PROCESSDEVELOPMENT PROCESS

Analysis Analysis creation of the creation of the Entity-Relationship ModelEntity-Relationship Model

DesignDesign Logical Database DesignLogical Database Design

creation of creation of normalized relationsnormalized relations Physical Database DesignPhysical Database Design

specification specification storage technology requirementsstorage technology requirements specification/ creation of specification/ creation of appropriate file structuresappropriate file structures

SchemasSchemas What are schemas?What are schemas? A schema describes the logical structure of a database.A schema describes the logical structure of a database. There are three levels of schemas:There are three levels of schemas:

1 Conceptual-level schemaConceptual-level schema2 External-level schemaExternal-level schema3 Internal-level schemaInternal-level schema

SchemasSchemas The conceptual-level schema is an organization-wide view of the The conceptual-level schema is an organization-wide view of the

entire database.entire database. The external-level schema consists of a set of individual user views The external-level schema consists of a set of individual user views

of portions of the database, also referred to as a of portions of the database, also referred to as a subschema.subschema. The internal-level schema provides a low-level view of the database.The internal-level schema provides a low-level view of the database.

AgendaAgenda Database Management–An IntroductionDatabase Management–An Introduction Relational DatabaseRelational Database Entity-Relationship DiagramEntity-Relationship Diagram

Relational DatabasesRelational Databases A A data modeldata model is an abstract representation of the contents is an abstract representation of the contents

of a database.of a database. The The relational data modelrelational data model represents everything in the represents everything in the

database as being stored in the form of tables.database as being stored in the form of tables. Technically, these tables are called Technically, these tables are called relationsrelations..

Basic Requirements of the Basic Requirements of the Relational Data ModelRelational Data Model

1 Primary keys must be unique.Primary keys must be unique.2 Every foreign key must either be null or have a value Every foreign key must either be null or have a value

corresponding to the value of a primary key in another relation.corresponding to the value of a primary key in another relation.3 Each column in a table must describe a characteristic of the Each column in a table must describe a characteristic of the

object identified by the primary key.object identified by the primary key.

Basic Requirements of the Basic Requirements of the Relational Data ModelRelational Data Model4 Each column in a row must be single-valued.Each column in a row must be single-valued.5 The value in every row of a specific column must The value in every row of a specific column must

be of the same data type.be of the same data type.6 Neither column order nor row order is significant.Neither column order nor row order is significant.

Accessing recordsAccessing records

Records are typically Records are typically updated, stored, and updated, stored, and retrieved using an identifier retrieved using an identifier called a called a primary keyprimary key– customer number for customer filecustomer number for customer file– invoice number for invoice fileinvoice number for invoice file– stock number for inventory filestock number for inventory file

Accessing RecordsAccessing Records A A secondary keysecondary key is another is another

field used to identify a recordfield used to identify a record Secondary keys do not uniquely Secondary keys do not uniquely

identify individual recordsidentify individual records Examples of secondary keysExamples of secondary keys

– invoice due dateinvoice due date– zip codezip code– bank customer last namebank customer last name

Accessing RecordsAccessing Records Foreign key:Foreign key:

attribute attribute (field) in one (field) in one table (record) table (record) that matches that matches primary key in primary key in another tableanother table

Used to link tables Used to link tables togethertogether

Relational DatabaseRelational Database

ProductProductNumberNumber

VendorVendor CodeCode

123467123467 ZDGZDG

243893243893 CFCCFC

277883277883 TBTTBT

476556476556 BBCBBC

775622775622 DFFDFF

Product TableProduct Table

Primary KeyPrimary Key

Foreign KeyForeign Key

VendorVendor CodeCode

ShipShip ModeMode

ACCACC TRKTRK

BADBAD ARPARP

BBCBBC TRKTRK

CACCAC UPSUPS

Vendor TableVendor Table Go to top ofVendor Table Go to top ofVendor Table

Searchsequentially until find ‘BBC”

Searchsequentially until find ‘BBC”

******

Relational DatabasesRelational Databases

FormalFormal TermTerm

LessLess Formal Formal TermTerm

DataDataProcessingProcessing TermTerm

relationrelation tabletable filefile

tupletuple rowrow recordrecord

attributeattribute columncolumn fieldfield

AgendaAgenda Database Management–An IntroductionDatabase Management–An Introduction Relational DatabaseRelational Database Entity-Relationship DiagramEntity-Relationship Diagram

ENTITY-RELATIONSHIP MODEL ENTITY-RELATIONSHIP MODEL (proposed by CHEN, 1976)(proposed by CHEN, 1976)

A detailed logical representation of data for an A detailed logical representation of data for an organization or business areaorganization or business area

Four Basic Constructs:Four Basic Constructs:-Entity-Entity-Relationship-Relationship-Attribute-Attribute-Cardinality (participation)-Cardinality (participation)

1.1. ENTITYENTITY: : Entities are named Entities are named objects in the universe of objects in the universe of discoursediscourse Types of entitiesTypes of entities

Thing (truck, building)Thing (truck, building) Person (customer, employee)Person (customer, employee) EventEvent

Instant duration (sale, purchase, cash Instant duration (sale, purchase, cash receipt)receipt)

Extended duration (month-long use of a Extended duration (month-long use of a truck, a course offering that starts on JAN 3 & truck, a course offering that starts on JAN 3 & ends on 15 May)ends on 15 May)

Concept (category of customer, course)Concept (category of customer, course) SYMBOL -- RectangleSYMBOL -- Rectangle

Customer Course offering

2. RELATIONSHIP 2. RELATIONSHIP : : Association Association between two (or more ?) entitiesbetween two (or more ?) entities

Examples:Examples: employee “assigned to” buildingemployee “assigned to” building customer “participates in” salecustomer “participates in” sale professor “teaches” course-professor “teaches” course-

offeringoffering

SYMBOL -- DiamondSYMBOL -- Diamond

Customer Saleparticipates

in

3. ATTRIBUTE 3. ATTRIBUTE : : Characteristics or elementary Characteristics or elementary properties of entities or relationships. They are properties of entities or relationships. They are used for actual communication about the real used for actual communication about the real world phenomena represented by entities or world phenomena represented by entities or relationshipsrelationships

Example attributes for the entity Example attributes for the entity INVENTORY:INVENTORY: stock#, color, price, cost, weightstock#, color, price, cost, weight

A primary key is a special attribute used to represent A primary key is a special attribute used to represent an instance of an entity or relationship in a databasean instance of an entity or relationship in a database Must be unique and universalMust be unique and universal Can be a concatenated (combined key)Can be a concatenated (combined key) ““No representation without identification”No representation without identification” For this class, we assume that relationships are For this class, we assume that relationships are

identified by the keys of their participating entitiesidentified by the keys of their participating entities SYMBOL – small connected circle (filled in for primary SYMBOL – small connected circle (filled in for primary

key)key)

InventoryStock# Color Price

4. Participation CARDINALITY (min, max): 4. Participation CARDINALITY (min, max): These show the correspondence of These show the correspondence of

entities entities and relationshipsand relationships

A Brel(min, max)

Entity “A” participates in relationship “rel” at a minimum of

- “0” times (optional)

- “1” time (mandatory)

Entity “A” participates in relationship “rel” at a maximum of

- “1” time (single time only)

- “n” times (many times)

4. Participation CARDINALITY (min, max): 4. Participation CARDINALITY (min, max): (other side of relationship)(other side of relationship)

A Brel(min, max)

Entity “B” participates in relationship “rel” at a minimum of

- “0” times (optional)

- “1” time (mandatory)

Entity “B” participates in relationship “rel” at a maximum of

- “1” time (single time only)

- “n” times (many times)

An ExampleAn Example Assuming two entities (EMPLOYEE and COURSE), draw an E-R Assuming two entities (EMPLOYEE and COURSE), draw an E-R

diagram for the following (sample data). Assume that diagram for the following (sample data). Assume that Employee_name and Course_titles are unique. Also assume other Employee_name and Course_titles are unique. Also assume other attributes such as Employee Address, and Course Credits.attributes such as Employee Address, and Course Credits.

Employee_nameEmployee_name Course_titleCourse_title Date_completedDate_completed Chen Chen C++C++ 06/9806/98 ChenChen JavaJava 09/9809/98 LisaLisa C++C++ 06/9806/98 LisaLisa SQLSQL 03/9903/99 TrinaTrina JavaJava 03/9803/98 HeikkiHeikki PerlPerl 06/9806/98 HeikkiHeikki JavaJava 09/9809/98 ……………….. …….……. ……..…….. ……………….. …….……. ……..……..

More ExamplesMore Examples A company has a number of employees. The attributes A company has a number of employees. The attributes

of EMPLOYEE include NAME, ADDRESS, and BIRTH-of EMPLOYEE include NAME, ADDRESS, and BIRTH-DATE. The company also has several projects. The DATE. The company also has several projects. The attributes of Project include PROJECT_CODE, attributes of Project include PROJECT_CODE, DESCRIPTION, and START_DATE. Each employee may DESCRIPTION, and START_DATE. Each employee may be assigned to one or more projects, or may not be be assigned to one or more projects, or may not be assigned to any project. A project is required to have at assigned to any project. A project is required to have at least one employee assigned, but may have several least one employee assigned, but may have several employees assigned.employees assigned.

A university has a large number of courses in its A university has a large number of courses in its catalog. Attributes of courses include CRS_NO, catalog. Attributes of courses include CRS_NO, CRS_NAME, and UNITS. Each course may have one or CRS_NAME, and UNITS. Each course may have one or more other courses as prerequisites, or may have no more other courses as prerequisites, or may have no prerequisite.prerequisite.

AssignmentAssignment

A college course may have one or more scheduled A college course may have one or more scheduled sections, or may not have a scheduled section. sections, or may not have a scheduled section. COURSE attributes include CRS_ID, CRS_NAME, COURSE attributes include CRS_ID, CRS_NAME, and UNITS. Attributes of SECTION include and UNITS. Attributes of SECTION include SECTION_NO and INSTRUCTOR.SECTION_NO and INSTRUCTOR.

A laboratory has several chemists who work on A laboratory has several chemists who work on various projects, and who may use certain kinds of various projects, and who may use certain kinds of equipment on each project. Attributes of CHEMIST equipment on each project. Attributes of CHEMIST include CHEMIST_ID, NAME, and PHONE. Attributes include CHEMIST_ID, NAME, and PHONE. Attributes of PROJECT include PROJ_ID and START_DATE. of PROJECT include PROJ_ID and START_DATE. Attributes of EQUIPMENT include EQUIP_NO and Attributes of EQUIPMENT include EQUIP_NO and COST.COST.

Topics DiscussedTopics Discussed

Database Management–An Database Management–An IntroductionIntroduction

Relational DatabaseRelational Database Entity-Relationship DiagramEntity-Relationship Diagram