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data base environment.lec 1
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INTRODUCTION TO DATABASES 1 © P r e n t i c e H a l l , 2 0 0 2
Transcript of data base environment.lec 1
INTRODUCTION TO DATABASES1
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CHAPTER 1:THE DATABASE ENVIRONMENT
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DEFINITIONS Data
Collection of raw facts and figures.
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Asad
5’ 10”
MaleShah
Ahsan6’ 2”
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DEFINITIONS Information
Processed form of data. Data can be processed in two ways
Structure and additional data
Summarize the data(diagrams and charts) 4
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Figure 1-1b Summarized dataUseful information that managers can use for decision making and interpretation
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DEFINITIONS Database
An organized collection of logically related data.
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Figure 1-1a Data in Context
Large volume of facts, difficult to interpret or make decisions based on
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DEFINITIONS Meta Data
They describe properties and characteristic of data.
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TRADITIONAL FILE PROCESSING SYSTEMS
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DISADVANTAGES OF FILE PROCESSING Program-Data Dependence
All programs maintain metadata for each file they use
Duplication of dataDifferent systems/programs have separate copies of the same data
Limited Data SharingNo centralized control of data
Lengthy Development TimesProgrammers must design their own file formats
Excessive Program Maintenance80% of information systems budget
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PROBLEMS WITH PROGRAM-DATA DEPENDENCY
It is the tight relationship between data stored in files and the specific programs required to update and maintain those files
Change in the file format affects both the program and the file
Lack of coordination and central control
Non-standard file formats
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PROBLEMS WITH DATA DUPLICATION
Waste of space to have duplicate dataCauses more maintenance headachesThe biggest Problem:
When data changes in one file, could cause inconsistencies
Compromises data integrity
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PROBLEMS WITH LIMITED DATA SHARING
Limited data for processingManagers face difficulty in generating reports
Incompatible files is separate systems
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PROBLEMS WITH DEVELOPMENT TIMES
The new application must follow the file pattern of the old system
Therefore, programmers prefer developing the program from scratch
System becomes static
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PROBLEMS WITH PROGRAM MAINTENANCE
Managing a non-centralized data is more difficult
All replicated data must be consistent
Therefore, more budget is required during maintenance
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SOLUTION: THE DATABASE APPROACH
Central repository of shared dataData is managed by a controlling agentStored in a standardized, convenient formEasy to store, manipulate and retrieve
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Requires a Database Management System (DBMS)
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DATABASE MANAGEMENT SYSTEM
A DBMS is a software program that manages a Database
It controls the organization, storage, management and retrieval of data in a database.
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DATABASE MANAGEMENT SYSTEM
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DBMS manages data resources like an operating system manages hardware resources
DBMS Databasecontainingcentralized shared data
Application#1
Application#2
Application#3
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ADVANTAGES OF DATABASE APPROACH Program-Data Independence
Metadata stored in DBMS, so applications don’t need to worry about data formats
Data queries/updates managed by DBMS so programs don’t need to process data access routines
Results in: increased application development and maintenance productivity
Minimal Data RedundancyLeads to increased data integrity/consistency
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ADVANTAGES OF DATABASE APPROACH Improved Data Sharing
Different users get different views of the data
Enforcement of StandardsAll data access is done in the same way
Improved Data Quality Constraints, data validation rules
Better Data Accessibility/ ResponsivenessUse of standard data query language (SQL)
Security, Backup/Recovery, ConcurrencyDisaster recovery is easier
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COSTS AND RISKS OF THE DATABASE APPROACH
Up-front costs:Installation Management Cost and Complexity
Conversion CostsOngoing Costs
Requires New, Specialized Personnel
Need for Explicit Backup and Recovery
Organizational ConflictOld habits die hard
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Figure 3Figure 1-3 Segment from enterprise data model
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Figure 3Figure 1-3 Segment from enterprise data model
One customer may place many orders, but each order is placed by a single customer One-to-many relationship
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Figure 3Figure 1-3 Segment from enterprise data model
One order has many order lines; each order line is associated with a single order One-to-many relationship
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Figure 3Figure 1-3 Segment from enterprise data model
One product can be in many order lines, each order line refers to a single product One-to-many relationship
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Figure 3Figure 1-3 Segment from enterprise data model
Therefore, one order involves many products and one product is involved in many orders Many-to-many relationship
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© Prenti ce Hall, 2002Figure 1-4 Order, Order_Line, Customer, and Product tables
Relationships established in special columns that provide links between tables
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DATABASE APPLICATIONPerforms series of actions on behalf of the database user.
CreateAdding new data to the database
ReadRetrieve data from current database
UpdateUpdate an existing data on database
DeleteRemove data from the database
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THE RANGE OF DATABASE APPLICATIONS
Personal Database – standalone desktop database Workgroup Database – local area network (<25 users)
Department Database – local area network (25-100 users)
Enterprise Database – wide-area network (hundreds or thousands of users)
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Figure 1-7 Typical data from a personal computer database
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Figure 1-8 Workgroup database with local area network
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Figure 1-9 An enterprise data warehouse
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COMPONENTS OF THE DATABASE ENVIRONMENT
CASE Tools – computer-aided software engineering Repository – centralized storehouse of metadata Database Management System (DBMS) – software for managing the database
Database – storehouse of the data Application Programs – software using the data User Interface – text and graphical displays to users Data Administrators – personnel responsible for maintaining the database
System Developers – personnel responsible for designing databases and software
End Users – people who use the applications and databases
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Figure 1-10 Components of the database environment
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EVOLUTION OF DB SYSTEMSFlat files - 1960s - 1980sHierarchical – 1970s - 1990sNetwork – 1970s - 1990sRelational – 1980s - presentObject-oriented – 1990s - presentObject-relational – 1990s - present
Data warehousing – 1980s - present
Web-enabled – 1990s - present
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