FILE ORGANIZATIONFILE ORGANIZATION
• BIT: Binary Digit (0,1;Y,N;On, Off)
• BYTE: Combination of BITS which represent a CHARACTER
• FIELD: Collection of BYTES which represent a Fact
• RECORD: Collection of FIELDS
which reflect a TRANSACTION
• FILE: A Collection of Similar
RECORDS
Managing Digital DataManaging Digital Data
The layout of a personnel file in traditional file organization.
FILE ORGANIZATIONFILE ORGANIZATION
• DATABASE:DATABASE: An Organization’s ElectronicAn Organization’s Electronic
Library of FILESLibrary of FILES
• Primary FIELD or Key:Primary FIELD or Key: Field in Each Field in Each Record Uniquely Identifies Record Uniquely Identifies
THIS Record ForTHIS Record For RETRIEVALRETRIEVAL UPDATINGUPDATING
SORTINGSORTING
• DATA REDUNDANCY• PROGRAM / DATA DEPENDENCY• LACK OF FLEXIBILITY• POOR SECURITY• LACK OF DATA SHARING & AVAILABILITY
TRADITIONAL FILE ENVIRONMENTTRADITIONAL FILE ENVIRONMENT ((FLAT FILEFLAT FILE))
Different information making up a student record retained in three different sites .
DATABASEDATABASE MANAGEMENTMANAGEMENT SYSTEMSYSTEM ((DBMSDBMS))
SOFTWARE TO CREATE & MAINTAIN DATA
*** *** ENABLES BUSINESS APPLICATIONS TO
EXTRACT DATA
*** INDEPENDENT OF SPECIFIC COMPUTER
PROGRAMS
DBMS
Managing Digital DataManaging Digital Data
• Traditional Files vs. Databases: Pros and Cons
– Traditional File Advantages• Simplicity• Efficiency• Customization
– Database Advantages• Reduced data redundancy• Application/data independence• Better control• Flexibility
COMPONENTSCOMPONENTS OFOF DBMSDBMS::
• THE SCHEMA: describe the structure of the
Database.DATA DEFINITION LANGUAGE:DATA DEFINITION LANGUAGE:
• Defines Data Elements in Database Defines Data Elements in Database • and Used to construct the schemaand Used to construct the schema
DATA MANIPULATION LANGUAGE:DATA MANIPULATION LANGUAGE:• Manipulates Data for ApplicationsManipulates Data for Applications
• DATA DICTIONARY:– Maintains all information supplied by the
developer when constructing the schema**
DBMS
Data definition language to create a schema in NOMAD
• Data Definition Language (DDL)Data Definition Language (DDL)
Components of Database Components of Database Management SystemsManagement Systems
• Data Manipulation Language (DML)Data Manipulation Language (DML)– Used to query the databaseUsed to query the database
Figure 8.14 A Paradox query by example
DATA DICTIONARY
A typical data dictionary for a staff file
• REDUCES COMPLEXITY
• REDUCES DATA REDUNDANCY
• CENTRAL CONTROL OF DATA DEFINITIONS
• REDUCES PROGRAM / DATA DEPENDENCE
• REDUCES DEVELOPMENT / MAINTENANCE COSTS
• ENHANCES SYSTEM FLEXIBILITY
• INCREASES ACCESS / AVAILABILITY OF INFORMATION
**
ADVANTAGESADVANTAGES OFOF DBMSDBMS::
DBMS
Database ModelsDatabase Models
– Records are related hierarchically – each category is a subcategory of the next level up
– Disadvantages of hierarchical databases• To retrieve a record, a user must start at the root and
navigate the hierarchy.
• If a link is broken, the entire branch is lost.
• Requires considerable data redundancy
HIERARCHICAL DATA MODELHIERARCHICAL DATA MODEL
ROOT
FIRST CHILD
2nd CHILD
RatingsRatings SalarySalary
CompensationCompensation JobJobAssignmentsAssignments
PensionPension InsuranceInsurance HealthHealth
BenefitsBenefits
EmployerEmployer
NETWORK DATA MODELNETWORK DATA MODEL
• VARIATION OF HIERARCHICAL MODELVARIATION OF HIERARCHICAL MODEL• Allows a record to be linked to more than one Allows a record to be linked to more than one
parentparent• USEFUL FOR MANY-TO-MANY USEFUL FOR MANY-TO-MANY
RELATIONSHIPSRELATIONSHIPS
NETWORKA
NETWORKB
NETWORKC
NETWORK1
NETWORK2
RELATIONAL DATA MODELRELATIONAL DATA MODEL
• Consists of tables; links among entities are Consists of tables; links among entities are maintained with maintained with foreign keysforeign keys
• DATA IN TABLE FORMATDATA IN TABLE FORMAT– RELATION: TABLE
– TUPLE: ROW (RECORD) IN TABLE
– FIELD: COLUMN (ATTRIBUTE) IN TABLE
*HOURS RATE TOTALABLE 40.50$ 10.35$ 419.18$
BAXTER 38.00$ 8.75$ 332.50$ CHEN 42.70$ 9.25$ 394.98$
DENVER 35.90$ 9.50$ 341.05$
TYPES OR RELATIONSTYPES OR RELATIONS
ONE-TO-ONE:ONE-TO-ONE: STUDENT ID
ONE-TO-MANY:ONE-TO-MANY:CLASS
STUDENTA
STUDENTB
STUDENTC
MANY-TO-MANY:MANY-TO-MANY:
STUDENTA
STUDENTB
STUDENTC
CLASS1
CLASS2
Relational OperationsRelational Operations
• Data Manipulation– Select :Select : is the selection of records that meets certain conditionis the selection of records that meets certain condition..– Project: Project: is the selection of certain columns from a table.is the selection of certain columns from a table.
– Join Join : : is the joining of data from multiple tables.is the joining of data from multiple tables.
• Structured Query Language (SQL)– International standard DDL and DML for relational
DBMS.– Advantages of using SQLAdvantages of using SQL
Users do not need to learn different DDLs and DMLs.
SQL can be embedded in widely used 3rd generation languages, increasing efficiency and effectiveness.
Programmer not forced to rewrite statements since SQL statements are portable.
Database Models
Advantages and disadvantages of database models
DatabaseDatabase ArchitectureArchitecture
• Shared Resource and Client/Server Shared Resource and Client/Server SystemsSystems
– Four basic client/server modelsFour basic client/server models
• Applications run at a server• Applications run on local PCs• Applications run on both the local PCs and the
server• Applications and key elements of the database
are split between the PCs and the server
Database ArchitectureDatabase Architecture
• Distributed DatabasesDistributed Databases– Replication :Replication :Full copy of the entire database is Full copy of the entire database is
stored at all sitesstored at all sites
A replicated database: each computer holds a copy of the entire database
Database ArchitectureDatabase Architecture– Fragmentation: Fragmentation: Parts of database are stored where they Parts of database are stored where they
are most often accessedare most often accessed
A fragmented database: each computer holds only the part of the database that is most frequently accessed by the local users
Web DatabasesWeb Databases
• Databases on the WebDatabases on the Web– CatalogsCatalogs– LibrariesLibraries– DirectoriesDirectories– Client lists and profilesClient lists and profiles
• When linking a database to the Internet, When linking a database to the Internet, considerconsider
• Which application to useWhich application to use• How to ensure Web surfers do not interfere with database How to ensure Web surfers do not interfere with database
updatesupdates• How to maintain securityHow to maintain security
Data WarehousingData Warehousing
• Data warehouseData warehouse– Collection of data that supports management Collection of data that supports management
decision makingdecision making– Phases in Building a Data WarehousePhases in Building a Data Warehouse
• Extraction PhaseExtraction Phase• Cleansing PhaseCleansing Phase• Loading PhaseLoading Phase
• Data MiningData Mining– Selecting, exploring, and modeling data to Selecting, exploring, and modeling data to discover discover
unknown relationshipsunknown relationships
DataData WarehousingWarehousing INFORMATION
DIRECTORY
INTERNALDATASOURCES
EXTERNALDATASOURCES
OPERATIONAL,HISTORICAL DATA
DATA WAREHOUSE
EXTRACT,TRANSFORM
DATAACCESS &ANALYSIS
QUERIES &REPORTS
OLAP
DATA MINING
Data-MiningData-Mining
Potential applications of data-mining
DATABASEDATABASE ADMINISTRATIONADMINISTRATION
• DEFINES & ORGANIZES DATABASE DEFINES & ORGANIZES DATABASE STRUCTURE AND CONTENTSTRUCTURE AND CONTENT
• DEVELOPS SECURITY PROCEDURESDEVELOPS SECURITY PROCEDURES• DEVELOPS DATABASE DOCUMENTATIONDEVELOPS DATABASE DOCUMENTATION• MAINTAINS DBMSMAINTAINS DBMS
**
Ethical and Societal IssuesEthical and Societal IssuesA Too-Risky Info HighwayA Too-Risky Info Highway
• Out of Hand -- Out of ControlOut of Hand -- Out of Control
– DBMSs allow organizations to collect, maintain, and sell vast amounts of private personal data easily.
• Where is the Information Going?Where is the Information Going?
– Many consumers provide information daily without being aware of where it is actually going.
– http://www.publicrecordfinder.com/
• The UpsideThe Upside– Database technology enables better and faster
services.
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