Relation database online version

Relation database online version - Relational Database...

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Unformatted text preview: Relational Database Agenda Database ManagementAn Introduction Relational Database Entity-Relationship Diagram Relation Data Model Conversion TYPICAL PROBLEMS WITH FILE-BASED SYSTEMS Organizational memory may be seen as a vast, disorganized data warehouse. Problems include: Redundancy: same data stored in different memories Data control: data not managed as a valuable resource Interface: difficult to access data Delays: long delays in responding to requests for data Lack of reality: data do not reflect the complexity of the real world Lack of data integration: data dispersed across different systems; also where data is stored may not be known. File-Oriented Approach Application program #2 Application program #1 File # 1 Item A Item B Item C File # 2 Item B Item D Item E DATABASE APPROACH TO MANAGING PERSISTENT DATA The database approach emphasizes the integration and sharing of data across the organization. Database Approach Application program #3 Application program #2 Database management system Application program #1 Item A Item B Item C Item D Item E Database BENEFITS OF THE DATABASE APPROACH Redundancy can be reduced Thus, inconsistency can be avoided Integration of data Data can be shared among applications Standards can be enforced by the DBA formats, representation, naming, documentation Security restrictions can be applied BENEFITS OF THE DATABASE APPROACH Data independence Broadly -- the immunity of applications to change in storage structure and access technique Logical -- capacity to change conceptual schema without changing application programs (e.g., adding an attribute or an entity type) Physical -- capacity to change internal schema without having to change external or conceptual schema (e.g., creating additional access structures to improve retrieval performance) Ease of Application Development Data accessibility and responsiveness enhanced Reduced program maintenance SOME DEFINITIONS What is a database? a shared collection of logically related persistent data , designed to meet the needs of multiple users usually within an organization. What is a database management system? DBMS is a collection of programs that enables users to define, construct and manipulate a database. (More detailed defn. later). What is a database system? STEPS IN DATABASE DEVELOPMENT PROCESS Analysis creation of the Entity-Relationship Model Design Logical Database Design creation of normalized relations Physical Database Design specification storage technology requirements specification/ creation of appropriate file structures Agenda Database ManagementAn Introduction Relational Database Entity-Relationship Diagram Relational Databases A data model is an abstract representation of the contents of a database....
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Relation database online version - Relational Database...

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