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Database System ComponentsDatabase System Components

The Database and the DBMSThe Database and the DBMS

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A Model of the Database A Model of the Database Processing SystemProcessing System

Hardware Programs Data Procedures People

Machine Human

Bridge

Instructions

Actors

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Database System ComponentsDatabase System Components

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User DataUser Data

Data aboutData about– Entities or objects Entities or objects

» employees, departments, products....employees, departments, products....» students, courses, professorsstudents, courses, professors

– Attributes Attributes » SS#, name, address, salary, departmentSS#, name, address, salary, department

– Relationships (bi-directional) between entities or objectsRelationships (bi-directional) between entities or objects» Employees Employees assigned to assigned to Departments.Departments.» Departments Departments are assignedare assigned Employees. Employees.» Students Students take take Courses.Courses.» Courses Courses are taken byare taken by Students. Students.

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Users’ DataUsers’ Data

For relational databases, tables with rows For relational databases, tables with rows and columns representing unique records and columns representing unique records and attributesand attributes

Not all tables are equally desirable: What is Not all tables are equally desirable: What is the problem with this?the problem with this?

Movie Rating Star

Saving Private Ryan G Tom Hanks

Saving Private Ryan G Matt Damon

Titanic R Kate Winslet

Titanic R Leonardo Di Caprio

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Relationships Between EntitiesRelationships Between Entities

CardinalityCardinality– the number of entities of each type that may the number of entities of each type that may

participate in the relationshipparticipate in the relationship– may be may be

» 1:1 (one-to-one)1:1 (one-to-one)

» 1:M (one-to-many)1:M (one-to-many)

» M:N (many-to-many)M:N (many-to-many)

– to determine cardinality, ask:to determine cardinality, ask:» for each A, how many B’s may be related?for each A, how many B’s may be related?

» for each B, how many A’s may be related?for each B, how many A’s may be related?

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Minimum & Maximum CardinalityMinimum & Maximum Cardinality

For each A, what is the minimum and maximum For each A, what is the minimum and maximum number of related B’s. number of related B’s.

For each B, what is the minimum and maximum For each B, what is the minimum and maximum number of related A’s. number of related A’s.

If the minimum is zeroIf the minimum is zero– The relationship is “The relationship is “optionaloptional.”.”

– The entity may or may not (The entity may or may not (sometimessometimes) participates ) participates

One or more One or more – The relationship is “mandatory.The relationship is “mandatory.

The entity must (The entity must (alwaysalways) participate. ) participate.

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Relationship ExamplesRelationship Examples

Business RulesBusiness Rules 1 : 1 (one-to-one)1 : 1 (one-to-one)

– Each faculty member is Each faculty member is alwaysalways assigned to assigned to oneone office. office.

– Each office is Each office is sometimessometimes assigned to assigned to oneone faculty member. faculty member. 1 : M (one-to-many)1 : M (one-to-many)

– Each employee is Each employee is alwaysalways assigned to assigned to one one department.department.

– Each department is Each department is alwaysalways assigned assigned manymany employees. employees. M : N (many-to-many)M : N (many-to-many)

– Each student Each student alwaysalways takes takes manymany courses. courses.

– Each course is Each course is sometimessometimes taken by taken by manymany students students

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What is the cardinality between...What is the cardinality between...

Cities and zip codes?Cities and zip codes?– Each city Each city ?? has has ?? zip codes. zip codes.

– Each zip code Each zip code ?? corresponds to only corresponds to only ?? city. city.

===> 1:M===> 1:M

People and phone numbers?People and phone numbers?– Each person Each person ?? has has ?? phone numbers. phone numbers.

– Each phone number Each phone number ?? belongs to ? persons. belongs to ? persons.

===> M:N===> M:N

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Four Data “Models”Four Data “Models”

HierarchicalHierarchical NetworkNetwork RelationalRelational Object OrientedObject Oriented

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HierarchicalHierarchical

Support 1:1 and 1:M RelationshipsSupport 1:1 and 1:M Relationships Parent - Child ViewpointParent - Child Viewpoint Parent (Owner) record has one or more Parent (Owner) record has one or more

children (Members)children (Members)– Customer has one checking accountCustomer has one checking account– Checking account has many transactionsChecking account has many transactions

Each child (member) has only one parent Each child (member) has only one parent (owner)(owner)

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Example Hierarchy: Banking DatabaseExample Hierarchy: Banking Database

Customer# | SS# | Address| ...

Checking Acct. # | Current Balance | Statement Date

Check# | Date | Payee | Amount

Deposit# | Date | Amount

Savings Acct. # | Current Balance | Statement Date

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Simple NetworkSimple Network

Children may have more than one parentChildren may have more than one parent Example: Joint checking accountExample: Joint checking account

John Dough Jayne Dough

Checking Acct. # 999

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Complex NetworkComplex Network

Supports M:N relationshipsSupports M:N relationships

Students

Courses Securities

Portfolios

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Relational ModelRelational Model

Data organized into tables (relations)Data organized into tables (relations) Tables have columns (attributes)Tables have columns (attributes) Data stored in rows (tuples)Data stored in rows (tuples) Each row has a unique Each row has a unique primaryprimary keykey Relationships included in the Relationships included in the datadata

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Relational Tables and DataRelational Tables and Data

EMPLOYEE(EMPLOYEE(SS#, SS#, EmployeeName, EmployeeAddress, EmployeeName, EmployeeAddress, Department_IDDepartment_ID))

DEPARTMENT(DEPARTMENT(DEPARTMENT_IDDEPARTMENT_ID, DepartmentName, Manager), DepartmentName, Manager)

EMPLOYEEEMPLOYEE

SS#SS# EmployeeNameEmployeeName Employee AddressEmployee Address Department_IDDepartment_ID

12231223 John DoughJohn Dough Wall StreetWall Street AcctAcct

32143214 Jayne DoughJayne Dough Wall StreetWall Street FinFin

76537653 Jill OutleyJill Outley WellbornWellborn AcctAcct

DEPARTMENTDEPARTMENT

DEPARTMENT_IDDEPARTMENT_ID DepartmentNameDepartmentName ManagerManager

AcctAcct AccountingAccounting Beane KounterBeane Kounter

FinFin Finance Finance Cash McCallCash McCall

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MetadataMetadata

““Data about the data.”Data about the data.” Data dictionary - Data Definition LanguageData dictionary - Data Definition Language

– For each table or recordFor each table or record» Table or record name Table or record name

» Number of columns or FieldsNumber of columns or Fields

» Primary keyPrimary key

– For each data itemFor each data item» Date item nameDate item name

» Data type (Numeric, date, text...)Data type (Numeric, date, text...)

» SizeSize

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MetadataMetadata

Use DDLUse DDL Description Description

of database of database structurestructure

System tables System tables (e.g., tables (e.g., tables and columns)and columns)

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IndexesIndexes

Usually “inverted lists” for accessing data.Usually “inverted lists” for accessing data.

DepartmentDepartment EmployeesEmployees

AcctAcct 1223, 76531223, 7653

FinFin 32143214

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Indexes and other data structuresIndexes and other data structures

Improve performance for sorting and Improve performance for sorting and searchingsearching

But: overhead of updatingBut: overhead of updating Who has Info Systems as major?Who has Info Systems as major?

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Application MetadataApplication Metadata

Structure & format of application Structure & format of application componentscomponents– FormsForms– ReportsReports– QueriesQueries– Etc.Etc.

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FormsForms

Data entryData entry Hiding IDsHiding IDs

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QueriesQueries

By example (QBE)By example (QBE) By formBy form By DML (Data Manipulation Language)By DML (Data Manipulation Language)

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ReportsReports

Data displayData display

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MenusMenus

Organize application componentsOrganize application components

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Application programsApplication programs

DMLsDMLs Standard Standard

languages + languages + DBMS DBMS interfaceinterface

Eg: trapping Eg: trapping events in events in Visual Basic Visual Basic + Access+ Access

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DBDBSystemSystemArchitectureArchitecture

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The Database SchemaThe Database Schema

TablesTables RelationshipsRelationships DomainsDomains

– constraints on values that a column may have.constraints on values that a column may have.

– e.g. date, integer number, text of length N...e.g. date, integer number, text of length N...

– ID’s (primary keys) must be uniqueID’s (primary keys) must be unique

Business rulesBusiness rules– Rules or policies that must be enforced in the database.Rules or policies that must be enforced in the database.

» Each employee is always assigned to one department.Each employee is always assigned to one department.

» Each department is always assigned one or more employees. Each department is always assigned one or more employees.

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SummarySummary

Database Systems includeDatabase Systems include– the database consisting ofthe database consisting of

» Data, Metadata, Indexes, Application metadataData, Metadata, Indexes, Application metadata

– the database management system (DBMS)the database management system (DBMS)» Design Tools & Run Time ToolsDesign Tools & Run Time Tools