CHAPTER 8: CHAPTER 8: MANAGING DATA MANAGING DATA

RESOURCES RESOURCES

File Organization Terms

• Field: group of characters that represent something

• Record: group of related fields• File: group of related records• Database: group of related files• Entity: a person, place, thing, event• Attribute: a piece of information about

an entity

Entities, Attributes & Key Fields

Traditional File Processing• Each functional area has specialized applications

• Each application requires an unique data file, that is often a subset of the master file

PROBLEMS WITH TRADITIONAL FILE PROCESSING

• Data integrity

• Data redundancy and confusion

• Program-data dependence

• Lack of flexibility

• Poor security

• Lack of data sharing and availability

The Database Approach

• Database– Collection of data organized to serve many

applications efficiently– Data is centralized – Uses a database management system (DBMS)

• Software to create and maintain a database

• Allows individual business applications to extract and use the data they require

Logical and Physical Views

• Physical view– How data are organized and stored on physical media

• Logical View– How the data appear to an application programmer or end

user

– Could be multiple logical views

• DBMS allows logical and physical views to be separated

Three components of DBMS

1. Data definition language• Defines each data element• Used by programmers in creating database

2. Data manipulation language• Used to manipulate data (e.g. SQL)

3. Data dictionary• Stores and organizes information about the

data

Types of Relations

ONE-TO-ONE: ONE-TO-ONE: STUDENT ID

MANY-TO-MANY:MANY-TO-MANY:

STUDENTA

STUDENTB

STUDENTC

CLASS1

CLASS2

ONE-TO-MANY: Department --> Faculty Member

Types of Databases

• Hierarchical DBMS– Older model– Treelike structure, one-to-many relationships

• Network DBMS– Also older model, allows many-to-many

relationships

• Neither are as flexible nor as easy to use as relational DBMS

Relational DBMS

Tables share a common data element

Basic Operations of Relational DBMS

• Select– Creates a subset of records that meet criteria

– E.g. all records (rows) with part number = 137

• Project– Creates a subset of columns

– Allows user to create new tables, or views, of data

• Join– Allows user to combine tables

– E.g. table of parts + supplier

Querying Databases: SQL

• SELECT– Lists the columns from tables that the user wants to see in the

result

• FROM– Identifies the tables from which the columns will be selected

• WHERE– Includes conditions for selecting specific rows (records)

Designing Databases

Entity-relationship diagram– A methodology for

documenting databases

– Illustrates relationships between entities

– Relationship can be • One-to-many

• One-to-one

• Many-to-many

NormalizationEliminates redundant data and awkward

relationships

Unnormalized relation for ORDER

Normalized relation for ORDER

Distributed Databases

• A database can be stored at more than one location• Parts or copies are physically stored in different

locations

Management Requirements

• Data Administration

• Data Planning and Modeling

• DataBase Administration

Data Warehouses & Datamining

• Extracts current & historical data from operational systems

• Combined with external data• Create database for analysis by management • Usually read only

Databases and the Web