File Organization Terms and Concepts

Bit: Smallest unit of data; binary digit (0,1) Byte: Group of bits that represents a single character, can be a letter, number, or another symbol Field: Grouping of characters into a word, group of word or complete number (such as person name or age)

Record: Group of related fields, such as student name, course taken, date, and grade

File: Group of records of same type

Database: Group of related files

Data Hierarchy in a Computer System

Low

High

Data redundancy

Poor security

Lack of data sharing and availability

Masalah dalam Lingkungan File Tradisional

Traditional File Processing

Data redundancy: duplicate data in multiple data files so that the same data are stored in more than place or location. Occure when different groups in an

organization independently collect the same pice of data and sore it independently of each other.

Lead to data inconsistency and waste storage resource

Poor of securityBecause there is little control of data management, who can access or disseminate information

Lack of data sharing and availability Information can’t flow freely across

different functional areas or different part of the organization

Rainer & Cegielski, 3/e, Wiley. Edited & revised by Zhang4-10

Jessup&Valacich: Database – a

collection of related data organized in a way to facilitate data searches

Laudon & Laudon:A database is A collection of data

Organized to efficiently serve many applications

by centralizing the data and

minimizing redundant data

Rainer & Cegielski, 3/e, Wiley. Edited & revised by Zhang4-11

DBMS – Database Management Systems It is a software used to

1. create, 2. store, 3. organize, 4. update, and 5. retrievedata, from a single database or several

databases [in a desirable arrangement/format, that

can be specified by the users in an easy way]

Database management system (DBMS)

software that permits an organization to centralize data, manage them efficiently, and provide access to the stored data by application program

interface between application programs and the physical data files

Rainer & Cegielski, 3/e, Wiley. Edited & revised by Zhang 4-13

Database management system (DBMS) provides all users with access to all the data.

DBMSs minimize the following problems:Data redundancyData isolationData inconsistency

DBMSs maximize the following issues:Data securityData integrityData independence

• Separates logical view and physical views of dataSeparates logical view and physical views of data• Logical viewLogical view: information focus on how users : information focus on how users

logically access information to meet their logically access information to meet their particular business needsparticular business needs

• Physical viewPhysical view: show how data actually organized : show how data actually organized on physical storage mediaon physical storage media

The Contemporary Database Environment

Types of Databases

• Relational DBMSRelational DBMS

• Hierarchical and Network DBMSHierarchical and Network DBMS

• Object-Oriented DatabasesObject-Oriented Databases

Entity: Person, place, thing, transaction, or event about which information is stored

Entity class: often called a table is collection of similar entityExample: A customer is an entity

Primary Concept of RDBS

Relational DBMS

Attribute: Description of a particular entity, also called fields or column, are characteristics or properties of an entity class

Example: A CUSTOMER entity can be described by a

Customer Number, First Name, Last Name, Street, City, State, Zip Code, Phone Number, Credit Card No, and Credit Card Exp

Key field: Identifier field used to retrieve, update, sort a record

Record: a collection of related attributes/fields about a single entity

Key field

Entities, Attributes (column, field), Key field

Rainer & Cegielski, 3/e, Wiley. Edited & revised by Zhang4-21

Entitities and Attributes (Laudon, w Zhang’s editing)

Fields

Value of attributes / fields

4345 02/09/01 1765 8 13.75

Records

• RDBMS DefinitionRDBMS Definition• Represents data as two-Represents data as two-

dimensional tables called relationsdimensional tables called relations

• Relates data across tables based on Relates data across tables based on common data elementcommon data element

• Examples: DB2, Oracle, MS SQL Examples: DB2, Oracle, MS SQL ServerServer

Relational Data Model

Three Basic Operations in a RDBMS

• Select:Select: Creates subset of rows that meet specific Creates subset of rows that meet specific criteriacriteria

• Join:Join: Combines relational tables to provide users Combines relational tables to provide users with informationwith information

• Project:Project: Enables users to create new tables Enables users to create new tables containing only relevant informationcontaining only relevant information

Three Basic Operations in a Relational Database

A row in a relation has the following properties:Only one value at the intersection of a column and row - a relation does not allow multi-valued attributes

Uniqueness - there are no duplicate rows in a relation

Key field: Identifier field used to retrieve (re-search), update, sort a recordPrimary key - a field (or group of

fields) that uniquely identifies a given entity in a table

Foreign key - a primary key of one table that appears as an attribute in another file and acts to provide a logical relationship between the two files

• Primary Key– A unique primary key makes it possible

to uniquely identify every row in a table– Primary key are provide way of

distinguishing each entity in a table– A primary key should never change and

cannot duplicated• Ex.: customer number

Foreign KeyWhen a table contains a column that is the

same as the primary key of a table, the column is called a foreign key

Foreign key - a primary key of one table that appears as an attribute in another file and acts to provide a logical relationship between the two files Ex.: item number

The use of identifiers represent relationships between entities

Hierarchical DBMSHierarchical DBMS

• One of type DBMSOne of type DBMS

• Organizes data in a tree-like structureOrganizes data in a tree-like structure

• Supports one-to-many parent-child Supports one-to-many parent-child relationshipsrelationships

Hierarchical DBMS