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Lesson OverviewLesson Overview

2.1 Basic Concept and 2.1 Basic Concept and VocabularyVocabulary

2.2 Database Approach: DBMS2.2 Database Approach: DBMS 2.3 Characteristic of DBMSs2.3 Characteristic of DBMSs 2.4 The Relationship Between 2.4 The Relationship Between

Application Programs And The Application Programs And The DBMSDBMS

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2.12.1 Basic Concept and VocabularyBasic Concept and Vocabulary

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2.1 Basic Concept and Vocabulary2.1 Basic Concept and Vocabulary

DatabaseDatabase FileFile Entity/ RecordsEntity/ Records Field/AttributeField/Attribute Key field:Key field:

Primary keyPrimary key Secondary keySecondary key Foreign keyForeign key

IndexIndex Data TypeData Type MetadataMetadata Data DictionaryData Dictionary

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The Hierarchy of DataThe Hierarchy of Data

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Data Entities, Attributes, and KeysData Entities, Attributes, and Keys

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Entities/RecordsEntities/Records Entities are Entities are anythinganything you want to you want to

store data aboutstore data about people (students, customers, people (students, customers,

employees, etc.)employees, etc.) places (resorts, cities, countries, etc.)places (resorts, cities, countries, etc.) things (restaurants, products, things (restaurants, products,

invoices, movies, paintings, books, invoices, movies, paintings, books, buildings, contracts, etc.)buildings, contracts, etc.)

events (elections, presentations, events (elections, presentations, earthquakes, hurricanes, etc.)earthquakes, hurricanes, etc.)

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Entity SetsEntity Sets

Entity sets are Entity sets are collectionscollections of of related entitiesrelated entities. Entities are . Entities are related by their classification:related by their classification:

student entities are related by the student entities are related by the fact that they are all studentsfact that they are all students

invoice entities are related by the invoice entities are related by the fact that they are all invoicesfact that they are all invoices

car entities are related by the fact car entities are related by the fact that they are all carsthat they are all cars

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Entity Sets, cont.Entity Sets, cont.

Entity sets are named after the entities that Entity sets are named after the entities that are stored in them.are stored in them.

Entity set names are singular.Entity set names are singular.Entity set names are capitalized.Entity set names are capitalized.

Examples:Examples:

An entity set named STUDENT contains An entity set named STUDENT contains student entities.student entities.

An entity set named INVOICE contains An entity set named INVOICE contains invoice entities.invoice entities.

An entity set named PRODUCT contains An entity set named PRODUCT contains product entities.product entities.

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Entity Sets, cont.Entity Sets, cont.

Entity sets can only contain Entity sets can only contain relatedrelated entitiesentities a a STUDENTSTUDENT entity set may not contain entity set may not contain

INVOICE entitiesINVOICE entities a a DEPARTMENTDEPARTMENT entity set may not contain entity set may not contain

invoice entitiesinvoice entities a a PRODUCTPRODUCT entity set may not contain entity set may not contain

employee entitiesemployee entities

……. And so on . And so on

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Entity Sets and EntitiesEntity Sets and Entities

Entity setsEntity sets are collections of are collections of related entitiesrelated entities

Unfortunately, database designers almost Unfortunately, database designers almost always use the two terms as synonyms. always use the two terms as synonyms.

When database designers refer to When database designers refer to entitiesentities, , they really are referring to they really are referring to entity setsentity sets. .

Therefore, when you see a reference to an Therefore, when you see a reference to an EMPLOYEEEMPLOYEE “entity” in a database design, “entity” in a database design, remember that remember that EMPLOYEEEMPLOYEE actually actually represents an entity set that contains a represents an entity set that contains a collection of employee entities.collection of employee entities.

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Database Table ContentsDatabase Table Contents

A database table is used to A database table is used to store an entity setstore an entity set An entity set is a collection of An entity set is a collection of

related entitiesrelated entities An entity is anything you want to An entity is anything you want to

keep track of, so an entity may be keep track of, so an entity may be a person, place, thing, event, etc.a person, place, thing, event, etc.

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Database Table ComponentsDatabase Table Components

At the At the conceptualconceptual level, a level, a database table may be viewed as a database table may be viewed as a matrix.matrix. Matrix rows are also known as Matrix rows are also known as tuplestuples

or or recordsrecords each row contains an entityeach row contains an entity

Matrix columns are also called Matrix columns are also called fieldsfields.. Each column (field) contains the Each column (field) contains the

entity’s attribute valuesentity’s attribute values

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Attributes/Field Attributes/Field

Attributes are the characteristics that Attributes are the characteristics that describe entities.describe entities.

Example: Example: a a studentstudent entity may be described by entity may be described by

attributes that may include his or attributes that may include his or her ... her ... social security numbersocial security number namename addressaddress date of birthdate of birth majormajor

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Attributes, cont.Attributes, cont.

Remember: Attributes are the Remember: Attributes are the characteristics that describe entities characteristics that describe entities

An invoice entity may be described An invoice entity may be described by attributes such as these:by attributes such as these: invoice numberinvoice number invoice dateinvoice date customer numbercustomer number invoice totalinvoice total

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Attribute NamesAttribute Names

Attribute names are capitalized.Attribute names are capitalized. For documentation reasons, For documentation reasons,

attribute names are composed attribute names are composed of two parts:of two parts: the first few characters reflect the the first few characters reflect the

entity they help describe. entity they help describe. subsequent characters are subsequent characters are

sufficiently descriptive to identify sufficiently descriptive to identify the attribute.the attribute.

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Attribute Names, cont.Attribute Names, cont.

Examples of attribute names:Examples of attribute names:

EMP_LNAME = employee last nameEMP_LNAME = employee last name

STU_GPA = student grade point STU_GPA = student grade point averageaverage

PROD_CODE = product codePROD_CODE = product code

CUST_LNAME = customer last nameCUST_LNAME = customer last name

INV_NUM = invoice numberINV_NUM = invoice number

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Key fieldKey field Primary Key (PK):Primary Key (PK):

An attribute (column), that uniquely identifies An attribute (column), that uniquely identifies each row in a database table.each row in a database table.

Cannot contains NULL valuesCannot contains NULL values Secondary Key:Secondary Key:

A non-PK search key, which may not yield A non-PK search key, which may not yield unique records. E.g.: the combination of first unique records. E.g.: the combination of first and last name may be a secondary key.and last name may be a secondary key.

Foreign Key (FK)Foreign Key (FK) An attribute (column) in a table that is a PK An attribute (column) in a table that is a PK

in another table. E.g.: in Order table, in another table. E.g.: in Order table, Customer_ID is a FK because it is a PK in Customer_ID is a FK because it is a PK in the Customer table.the Customer table.

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Entity IntegrityEntity Integrity

A table exhibits entity integrity when all of itsPrimary Key (PK) values uniquely identify eachtable row (record.)

EMPLOYEE table

1. A PK cannot contain duplicate values2. A PK cannot contains nulls

Note: A null indicates the absence of a value; it is not a blank. (You create a null when you tap the ENTER key without first making an entry. A blank is created when you tap the space bar and then tap the ENTER key.)

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Foreign keys (FK) Foreign keys (FK) and Referential Integrityand Referential Integrity

To maintain referential integrity, a foreign key (FK) must reference an existing PK value in a related table or it may be null.

A Foreign Key (FK) is an attribute located in one table that “points to” a Primary Key (PK) in a related table. The use ofFKs allows you relate one table to another.

INVOICE table

LINE table

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IndexIndex

A secondary file structure that A secondary file structure that provides an alternative path to the provides an alternative path to the data.data.

A sorted list of A sorted list of key valueskey values from the from the original table along with a pointer original table along with a pointer to the rest of the data in each row. to the rest of the data in each row.

Used to speed up searches and Used to speed up searches and data retrieval.data retrieval.

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Data TypeData Type

The data characteristic that The data characteristic that determines how the filed values determines how the filed values can be used.can be used.

Example:Example: An employee name is properly An employee name is properly

defined to be a text data type.defined to be a text data type. An employee birthday is defined as An employee birthday is defined as

date data typedate data type E.g.: text, numeric, date, currency, E.g.: text, numeric, date, currency,

OLE objectOLE object

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MetadataMetadata

Data about dataData about data Data that describe other data Data that describe other data

including the source, use, value and including the source, use, value and meaning of the datameaning of the data

Typically stored in a data dictionaryTypically stored in a data dictionary E.g.: E.g.: Data Item Name Data Type Length in

Characters (bytes) Name Text 30

Stud_No Numeric 6

Class Text 4

Major Text 4

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Data DictionaryData Dictionary

A compilation of the metadataA compilation of the metadata A special database that describe A special database that describe

individual databases and its individual databases and its environment. environment.

Contains data descriptors called Contains data descriptors called metadata that define source, the metadata that define source, the use, the value and the meaning use, the value and the meaning of data.of data.

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2.12.1Database Approach: DBMSDatabase Approach: DBMS

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Fig 5.3Fig 5.3

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Problems with the “Traditional” Problems with the “Traditional” ApproachApproach

Example: Example: Students registration Students registration Students library Students library Students Industrial training Students Industrial training Students graduationStudents graduation

Data redundancyData redundancy Program-data dependenceProgram-data dependence InflexibilityInflexibility

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Database ApproachDatabase Approach

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Table 5.1Table 5.1

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Table 5.2Table 5.2

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Database Management Systems Database Management Systems (DBMSs)(DBMSs)

Provide a user viewProvide a user view Provide tools to create & modify Provide tools to create & modify

the databasethe database Store & retrieve dataStore & retrieve data Manipulate dataManipulate data Produce reportsProduce reports

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Fig 5.15Fig 5.15

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Fig 5.16Fig 5.16

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Fig 5.17Fig 5.17

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Database Management System Database Management System (DBMS) “The Tools”(DBMS) “The Tools”

Define – Define – specify data types, structures and specify data types, structures and constraintsconstraints

Construct – Construct – initial creation and populationinitial creation and population

Manipulate – Manipulate – run queries, Alter table run queries, Alter table definitions, insert/delete recordsdefinitions, insert/delete records

Share – Share – Concurrent access, Concurrent access,

Protect – Protect – from system malfunction or from system malfunction or malicious attacksmalicious attacks

Maintain – Maintain – As requirements change, so As requirements change, so should the system.should the system.

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What DBMS have you heard What DBMS have you heard of?of? __________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

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Mainstream DBMSsMainstream DBMSs Oracle - Oracle - Oracle corporationOracle corporation

www.oracle.com DB2 - DB2 - IBMIBM

http://www-306.ibm.com/software/data/db2/udb/ ACCESS, SQL Server - ACCESS, SQL Server - MicrosoftMicrosoft

http://www.microsoft.com/Office/Access/prodinfo/ Adaptive Server Enterprise (ASE) - Adaptive Server Enterprise (ASE) -

SybaseSybase http://www.sybase.com/products/databaseservers/ase

MySQL - MySQL - MySQL Open sourceMySQL Open source http://www.mysql.com/

PostgreSQL –PostgreSQL – Global Development Global Development Group Group http://advocacy.postgresql.org/

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Oracle Oracle Ideal for large scale grid and cluster computingIdeal for large scale grid and cluster computing Currently pushing toward small business, Currently pushing toward small business,

single computer serverssingle computer servers Many Enterprise applications are available or Many Enterprise applications are available or

includedincluded Finance managementFinance management Human Resource ManagementHuman Resource Management MarketingMarketing Product lifecycle managementProduct lifecycle management On and on and on...On and on and on...

43% market share43% market share

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DB2DB2

Flexible to install on a wide Flexible to install on a wide variety of systemsvariety of systems

Focuses on the integration of Focuses on the integration of other DBMS. other DBMS.

Data can be distributed.Data can be distributed. Has many application packages, Has many application packages,

similar to Oraclesimilar to Oracle 24% Market Share24% Market Share

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SQL ServerSQL Server

Targets small businessTargets small business Easy to installEasy to install Low cost of ownershipLow cost of ownership Excellent SupportExcellent Support Notoriously insecure Notoriously insecure

Susceptible to virus and worm attacksSusceptible to virus and worm attacks New patches released monthlyNew patches released monthly

17% Market Share17% Market Share

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Adaptive Server Enterprise (ASE) Adaptive Server Enterprise (ASE) - Sybase- Sybase

Low resource requirementsLow resource requirements Fast and reliableFast and reliable Lower cost of ownership Lower cost of ownership

compared to Oracle or DB2compared to Oracle or DB2 Popular on Wall Street due to its Popular on Wall Street due to its

high transaction ratehigh transaction rate 2% Market Share2% Market Share

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MySQL MySQL

Open source DBMSOpen source DBMS Supported by a for-profit company Supported by a for-profit company Well known compared to other Well known compared to other

open source solutions.open source solutions. Offers free GPL version and a Offers free GPL version and a

licensed version that includes licensed version that includes vendor support.vendor support.

Less popular and less scalable Less popular and less scalable than Oracle, DB2 or ASEthan Oracle, DB2 or ASE

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PostgreSQLPostgreSQL

Open Source DBMSOpen Source DBMS Developed (originally) at the Developed (originally) at the

University of California, BerkeleyUniversity of California, Berkeley Supported by a non-for-profit Supported by a non-for-profit

organization: organization: PostgreSQL – PostgreSQL – Global Development GroupGlobal Development Group

More developed and robust than More developed and robust than MySQLMySQL

Less popular in the business Less popular in the business worldworld

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DBMS vs. Custom applicationDBMS vs. Custom application

DatabaseDefinition

(meta-data)

StoredData

Software to Process Queries

Software to Access Stored Data

User Interface User Interface/Software to

Process Queries/Software to Access

Stored Data

StoredData

UsersDatabase approach Custom App.

DBMS software

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2.32.3 Characteristic of DBMSsCharacteristic of DBMSs

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Characteristics of the Database Characteristics of the Database ApproachApproach

1.1. Self DescribingSelf Describing A catalog keeps track of the A catalog keeps track of the

database structuredatabase structure Contains a description of its own Contains a description of its own

structure called a structure called a data dictionary, data dictionary, data directory, metadatadata directory, metadata

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SelfSelf DescribingDescribing

.1.1Catalog allows freedom to choose DBMSCatalog allows freedom to choose DBMS

DatabaseDefinition

(meta-data)

StoredData

Software to Process Queries

Software to Access Stored Data

User Interface

Software to Process Queries

Software to Access Stored Data

choice 1 choice 2

...Software to

Process Queries

Software to Access Stored Data

choice n

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Self DescribingSelf Describing

.1.1One DBMS can access several independent databasesOne DBMS can access several independent databases

Meta-Data1

StoredData

1

User Interface

Software to Process Queries

Software to Access Stored Data

Meta-Data2

StoredData

2

University DB Matchmaker DB

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Characteristics of the Database Characteristics of the Database ApproachApproach

1.1. Self DescribingSelf Describing A catalog keeps track of the A catalog keeps track of the

database structuredatabase structure

2.2. Program/Data IndependenceProgram/Data Independence Allows program to be modified Allows program to be modified

without changing the file without changing the file structure.structure.

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Program/Data IndependenceProgram/Data Independence

DBMS Custom App.

User Interface User Interface

Catalog

Name AgeGender

Name AgeGender

Client:

Client:

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Program/Data IndependenceProgram/Data Independence

DBMS Custom App.

User Interface User Interface

Catalog

Name AgeGender

Name AgeGender

Height

Height

Client:

Client:

Is the existence of a catalog sufficient for program data independence?

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Characteristics of the Database Characteristics of the Database ApproachApproach

1.1. Self DescribingSelf Describing A catalog keeps track of the A catalog keeps track of the

database structuredatabase structure

2.2. Program/Data IndependenceProgram/Data Independence

3.3. Multiple ViewsMultiple Views View=Virtual TableView=Virtual Table

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ViewsViews

Internal (Physical) Tables

Conceptual tables

...View 1 View 2 View 3 View n

User Interface, variety of users

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When would multiple views be When would multiple views be useful?useful?

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

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Example Views – Matchmaker Example Views – Matchmaker DBDB

Client ID Name Phone email Gender Age123 Edward 223-4432 ed@nd.edu M 20574 Sally 394-0293 sal@nd.edu F 22

My Info Name Phone email Gender AgeEdward 223-4432 ed@nd.edu M 20

Brows Others Name email Gender Age Hobby1 Hobby2 Avg RatingEdward ed@nd.edu M 20 Baseball 1Sally sal@nd.edu F 22 Baseball Drawing 5

DBA view (logical table)

Owning client’s view (virtual table)

View to brows other client’s info. (virtual table)

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Characteristics of the Database Characteristics of the Database ApproachApproach

1.1. Self DescribingSelf Describing A catalog keeps track of the database structureA catalog keeps track of the database structure

2.2. Program/Data IndependenceProgram/Data Independence

3.3. Multiple ViewsMultiple Views View=Virtual TableView=Virtual Table

4.4. Data Integration - Pooling the files in a centralized locationData Integration - Pooling the files in a centralized location Data Sharing - Allows all authorized users access through data integrationData Sharing - Allows all authorized users access through data integration Minimum Data Duplication Or Redundancy - Maintaining System integrity, Minimum Data Duplication Or Redundancy - Maintaining System integrity,

efficiency and reliabilityefficiency and reliability

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2.42.4 The Relationship Between The Relationship Between Application Programs And The DBMSApplication Programs And The DBMS

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The Relationship Between Application The Relationship Between Application Programs And The DBMSPrograms And The DBMS

A User Interacts with a A User Interacts with a Application with Database Application with Database

The Application Interfaces The Application Interfaces with the DBMSwith the DBMS

The DBMS accesses the The DBMS accesses the DatabaseDatabase

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Actors/UsersActors/Users

DevelopersDevelopers DBADBA DesignerDesigner System AnalystSystem Analyst ProgrammerProgrammer

End userEnd user ParametricParametric CasualCasual SophisticatedSophisticated

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The Relationship Between Application The Relationship Between Application Programs And The DBMS -Continue ...Programs And The DBMS -Continue ...

At one time application programs and At one time application programs and the DBMS were clearly distinctthe DBMS were clearly distinct

Application Programs were written In Application Programs were written In 3GL such as COBOL in the past.3GL such as COBOL in the past.

Currently all 4Currently all 4thth GL or web-based GL or web-based development tools can associate with development tools can associate with DBMS. DBMS.

These Application Programs called These Application Programs called upon the DBMS for management upon the DBMS for management services.services.

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USER

DatabaseApplications

DBMS Database

The Relationship Between Application The Relationship Between Application Programs And The DBMS -ContinuePrograms And The DBMS -Continue... ...

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SummarySummary Basic Concept and VocabularyBasic Concept and Vocabulary

DatabaseDatabase FileFile Entity/ RecordsEntity/ Records Field/AttributeField/Attribute Key field:Key field: Primary keyPrimary key Secondary keySecondary key Foreign keyForeign key IndexIndex Data TypeData Type MetadataMetadata Data DictionaryData Dictionary

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SummarySummary

Characteristic of DBMSsCharacteristic of DBMSs1.1. Self DescribingSelf Describing

2.2. Program/Data IndependenceProgram/Data Independence

3.3. Multiple ViewsMultiple Views

4.4. Data IntegrationData Integration

The Relationship Between The Relationship Between Application Programs And The Application Programs And The DBMSDBMS