Mgt 20600: Mgt 20600: IT Management & ApplicationsIT Management & Applications

DatabasesDatabases

TuesdayTuesday

April 4, 2006April 4, 2006

RemindersReminders ReadingReading

– For todayFor today Fundamentals text, Chapter Three, Organizing Data Fundamentals text, Chapter Three, Organizing Data

and Informationand Information– For next class on April 11For next class on April 11thth

Fundamentals text, Chapter Six, Information and Decision Fundamentals text, Chapter Six, Information and Decision Support SystemsSupport Systems

HomeworkHomework– Homework FourHomework Four

DatabasesDatabases Due Thursday, April 14thDue Thursday, April 14th

Next week: Decision Support SystemsNext week: Decision Support Systems

DatabasesDatabases

A well-designed and well-managed A well-designed and well-managed database is an extremely valuable tool in database is an extremely valuable tool in supporting decision makingsupporting decision making

Databases are key corporate assetsDatabases are key corporate assets Databases are the foundation for Databases are the foundation for

sophisticated analyses that provide sophisticated analyses that provide business intelligencebusiness intelligence– What new products to designWhat new products to design– How to market to particular customer groupsHow to market to particular customer groups– Which customer groups are the most profitableWhich customer groups are the most profitable

Traditional Approach Traditional Approach to Data Managementto Data Management

Traditional approach: separate data files are created for each application

Results in data redundancy (duplication)

Data redundancy conflicts with data integrity

Database Approach Database Approach to Data Managementto Data Management

Database approach: pool of related data is shared by multiple applications

Significant advantages over traditional approach

Advantages of Database ApproachAdvantages of Database Approach

Improved strategic use of dataImproved strategic use of data Reduced data redundancyReduced data redundancy Improved data integrityImproved data integrity Easier modification and updatingEasier modification and updating Data and program independenceData and program independence Better access to data and informationBetter access to data and information Standardization of data accessStandardization of data access A framework for program developmentA framework for program development Better overall protection of the dataBetter overall protection of the data Shared data and information resourcesShared data and information resources

Disadvantages of the Disadvantages of the Database ApproachDatabase Approach

More complexityMore complexity More difficult to recover from a More difficult to recover from a

failurefailure More expensiveMore expensive

DatabasesDatabases

Databases must containDatabases must contain– Accurate informationAccurate information– Right kinds of informationRight kinds of information– Current informationCurrent information– Information from all organizational Information from all organizational

functionsfunctions

Database DataDatabase Data

Data regardingData regarding– Important entitiesImportant entities

CustomersCustomers SuppliersSuppliers TransactionsTransactions

– Each entity will have a number of attributes Each entity will have a number of attributes about which you want to collect and store about which you want to collect and store informationinformation

Customer addressCustomer address Customer phone numberCustomer phone number Customer account numberCustomer account number

Entities, Attributes, KeysEntities, Attributes, Keys

Entity: a generalized class of people, places, or things (objects) for which data is collected, stored, and maintained (Table and records)Attribute: a characteristic of an entity (fields)Data item: a value of an attribute (fields)Key: field(s) that identify a recordPrimary key: field(s) that uniquely identify a record

Hierarchy of DataHierarchy of Data

Field: name, number, or characters that describe an aspect of a business object or activityRecord: a collection of related data fieldsFile: a collection of related recordsDatabase: a collection of integrated and related files

Data Modeling and the Data Modeling and the Relational Database ModelRelational Database Model

When building a database, consider:When building a database, consider:– Content: What data should be collected, Content: What data should be collected,

at what cost?at what cost?– Access:Access: What data should be provided to What data should be provided to

which users, and when?which users, and when?– Logical structure:Logical structure: How should data be How should data be

arranged to make sense to a given user?arranged to make sense to a given user?– Physical organization:Physical organization: Where should Where should

data be physically located?data be physically located?

Data ModelingData Modeling

Building a database requires two Building a database requires two types of designtypes of design– Logical designLogical design

Shows an abstract model of how data should Shows an abstract model of how data should be structured and arranged to meet an be structured and arranged to meet an organization’s information needsorganization’s information needs

– Physical designPhysical designFine-tunes the logical database design for Fine-tunes the logical database design for

performance and cost considerationsperformance and cost considerations

Data ModelingData Modeling

Data model: Data model: a diagram of data a diagram of data entities and their relationshipsentities and their relationships

Entity-relationship (ER) Entity-relationship (ER) diagrams: diagrams: data models that use data models that use basic graphical symbols to show the basic graphical symbols to show the organization of and relationships organization of and relationships between databetween data

Data ModelingData Modeling

An Entity-Relationship (ER) Diagram for a Customer Order DatabaseAn Entity-Relationship (ER) Diagram for a Customer Order Database

The Relational Database ModelThe Relational Database Model

Relational model: Relational model: all data elements are all data elements are placed in two-dimensional tables placed in two-dimensional tables (relations), which are the logical (relations), which are the logical equivalent of filesequivalent of files

In the relational model:In the relational model:– Each table represents a data entityEach table represents a data entity– Each row of a table represents a specific Each row of a table represents a specific

instance of a data entityinstance of a data entity– Columns of the table represent attributesColumns of the table represent attributes

The Relational Database ModelThe Relational Database Model

A Relational Database ModelA Relational Database Model

Creating and Modifying the Creating and Modifying the DatabaseDatabase

Data definition language (DDL)Data definition language (DDL)– Collection of instructions/commands that Collection of instructions/commands that

define and describe data and data define and describe data and data relationships in a databaserelationships in a database

– Allows database creator to describe the data Allows database creator to describe the data and the data relationships that are to be and the data relationships that are to be contained in the schema and the subschemascontained in the schema and the subschemas

Data dictionary: Data dictionary: a detailed description of a detailed description of all the data used in the databaseall the data used in the database

Storing and Retrieving DataStoring and Retrieving Data

Logical and Physical Access PathsLogical and Physical Access Paths

Providing a User ViewProviding a User View Schema: Schema: description of the entire description of the entire

databasedatabase User view: User view: user-accessible portion of user-accessible portion of

the databasethe database SubschemaSubschema

– Contains a description of a subset of the Contains a description of a subset of the databasedatabase

– Identifies which users can view and modify Identifies which users can view and modify the data items in the subsetthe data items in the subset

– Is used to create different user viewsIs used to create different user views

Providing a User ViewProviding a User View

The Use of Schemas and SubschemasThe Use of Schemas and Subschemas

Creating and Modifying Creating and Modifying the Databasethe Database

A Typical Data Dictionary EntryA Typical Data Dictionary Entry

Manipulating Data and Manipulating Data and Generating ReportsGenerating Reports

Data manipulation language (DML): Data manipulation language (DML): commands that manipulate the data in a commands that manipulate the data in a databasedatabase– Query-By-Example (QBE): Query-By-Example (QBE): a visual approach a visual approach

to developing database queries or requeststo developing database queries or requests– Structured Query Language (SQL): Structured Query Language (SQL): ANSI ANSI

standard query language for relational standard query language for relational databasesdatabases

– Database programs can produce reports, Database programs can produce reports, documents, and other outputsdocuments, and other outputs

Manipulating DataManipulating Data

Selecting: Selecting: eliminates rows eliminates rows according to criteriaaccording to criteria

Projecting: Projecting: eliminates columns in a eliminates columns in a tabletable

Joining: Joining: combines two or more combines two or more tablestables

Linking: Linking: relates or links two or more relates or links two or more tables using common data attributestables using common data attributes

Manipulating DataManipulating Data

Linking Data Tables to Answer an InquiryLinking Data Tables to Answer an Inquiry

Database AdministrationDatabase Administration

Database administrator (DBA):Database administrator (DBA): directs or performs all activities to directs or performs all activities to maintain a database environmentmaintain a database environment– Designing, implementing, and Designing, implementing, and

maintaining the database system and maintaining the database system and the DBMSthe DBMS

– Establishing policies and proceduresEstablishing policies and procedures– Training employeesTraining employees

Selecting a Database Selecting a Database Management SystemManagement System

Important characteristics of databases Important characteristics of databases to consider:to consider:– Size of the databaseSize of the database– Number of concurrent usersNumber of concurrent users– PerformancePerformance– Ability to be integrated with other systemsAbility to be integrated with other systems– Features of the DBMSFeatures of the DBMS– Vendor considerationsVendor considerations– Cost of the systemCost of the system