chapter 8: managing data resources. file organization terms field: group of characters that...
TRANSCRIPT
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