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Chapter 1
Introduction to Databases
Transparencies
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Chapter 1 - Objectives
x Some common uses of database systems.x Characteristics of file-based systems.x Problems with file-based approach.x Meaning of the term database.x Meaning of the term Database Management
System (DBMS).
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Chapter 1 - Objectives
x Typical functions of a DBMS.x Major components of the DBMS environment.x Personnel involved in the DBMS environment.x History of the development of DBMSs.x Advantages and disadvantages of DBMSs.
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File-Based Processing
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Limitations of File-Based Approach
x Data dependence File structure is defined in the program code.
x Incompatible file formats Programs are written in different languages, and so
cannot easily access each others files.
x
Fixed Queries/Proliferation of applicationprograms Programs are written to satisfy particular
functions. Any new requirement needs a new program.
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Database Approach
x Arose because: Definition of data was embedded in application
programs, rather than being stored separately andindependently.
No control over access and manipulation of databeyond that imposed by application programs.
x Result: the database and Database Management System
(DBMS).
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Database
x Shared collection of logically related data (anda description of this data), designed to meet theinformation needs of an organization.
x System catalog (metadata) provides descriptionof data to enable programdata independence.
x Logically related data comprises entities,attributes, and relationships of anorganizations information.
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Database Management System (DBMS)
x A software system that enables users to define,create, maintain, and control access to thedatabase.
x (Database) application program: a computerprogram that interacts with database by
issuing an appropriate request (SQLstatement) to the DBMS.
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Database Management System (DBMS)
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Database Approach
x Data definition language (DDL). Permits specification of data types, structures and
any data constraints.
All specifications are stored in the database.
x Data manipulation language (DML).
General enquiry facility (query language) of thedata.
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Database Approach
x Controlled access to database mayinclude: a security system an integrity system a concurrency control system a recovery control system a user-accessible catalog.
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Views
x Allows each user to have his or her own view of the database.
x A view is essentially some subset of thedatabase.
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Components of DBMS Environment
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Components of DBMS Environment
x Hardware Can range from a PC to a network of
computers.
x Software DBMS, operating system, network software (if
necessary) and also the application programs.x Data
Used by the organization and a descriptionof this data called the schema.
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Components of DBMS Environment
x Procedures Instructions and rules that should be applied to
the design and use of the database and DBMS.x People
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Roles in the Database Environment
x Data Administrator (DA )x Database Administrator (DBA)x
Database Designers (Logical and Physical)x Application Programmersx End Users (naive and sophisticated)
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History of Database Systems
x First-generation Hierarchical and Network
x Second generation Relational
x Third generation Object-Relational Object-Oriented
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Advantages of DBMSs
x Control of data redundancyx Data consistencyx More information from the same amount of
datax Sharing of datax Improved data integrityx Improved securityx Enforcement of standardsx Economy of scale
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Advantages of DBMSs
x Balance conflicting requirementsx Improved data accessibility and responsivenessx Increased productivityx Improved maintenance through data
independencex Increased concurrencyx Improved backup and recovery services
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Disadvantages of DBMSs
x Complexityx Sizex Cost of DBMSx Additional hardware costsx Cost of conversionx Performancex Higher impact of a failure
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