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An Introduction to database system

An Introduction to database system. Basic Definitions. Data: Meaningful facts, text, graphics, images, sound, video segments. Database: An organized collection of logically related data. Information: Data processed to be useful in decision making. Metadata: Data that describes data.

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An Introduction to database system

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  1. An Introduction to database system

  2. Basic Definitions • Data: Meaningful facts, text, graphics, images, sound, video segments. • Database: An organized collection of logically related data. • Information: Data processed to be useful in decision making. • Metadata: Data that describes data.

  3. What is a DataBase system?(DB) • It is a logically coherent collection of data with inherent meaning. • It represents a miniworld, and should represent the state of that world accurately. • It is managed by a database management system (DBMS).

  4. What is a DataBase Management System?(DBMS) • A (large) piece of software which provides an interface between the user or application program and the stored data. • A DBMS is developed according to a particular data model. • Some example DBMSs are: • IMS, DB2, Oracle, Sybase, Informix, SQL Server, Access, FoxPro, O2.

  5. The functionality of DBMS • Manages very large amounts of data. • Supports efficient access to very large amounts of data. • Supports concurrent access to very large amounts of data. • Supports secure, atomic access to very large amounts of data.

  6. Several basic concepts • Data models • A data model is a way of representing (part of) the world. • The principle current data model are: • Hierarchical • Network • Relational • Object-oriented • E-R • Semantic

  7. Several basic concepts • Database design • Design goals • Minimize redundancy in order to eliminate the modification anomalies in database. • Represent the situation accurately • Design Stages • Conceptual (product independent) • Logical (product specific) • Physical / Implementation (product specific)

  8. The stages focused in COP4540 Database Development Activities

  9. Conceptual Database Modeling • Determine user requirements. • Determine business rules. • Build conceptual data model • outcome is an entity-relationship diagram or similar communication tool.

  10. Logical Database Design • Select logical database model. • Map Entity-Relationship Diagrams • Normalize data structures. • Specify business rules.

  11. Physical Database Design • Select DBMS • Select storage devices • Determine access methods • Design files and indexes • Determine database distribution • Specify update strategies

  12. Several basic concepts • Schema • Logical structure of the data defined by using data definition language (DDL). • Queries • A “query” is a database lingo for a question about the data. • A “query” is composed by using query language (QL)

  13. The architecture of database system Users / Programmers Application Programs / Queries 1. Software to process queries/programs 2. Software to access stored data Database Management System Stored data

  14. Components of the Database Environment • CASE Tools • Repository • Database Management System (DBMS) • Database • Application Programs • User Interface • Database Administrators (DBA) • System Developers • End Users

  15. Evolution of Database Systems • Hierarchical and Network (Legacy): Data are modeled as linked records. • Relational: Data are modeled as related tables. • Object-oriented: Data are organized as linked objects. • Object-relational: Integration of relational and object-oriented features.

  16. RDBMS and SQL • RDBMS is a DBMS on the basis of relational model. • It is the most popular type of the DBMS. • The data is organized as tables called relations • Two famous systems: • System R at IBM & Ingres at UC Berkeley • SQL (Structured Query Language) • the most important query language based on relational model.

  17. RDBMS and SQL Accounts SELECT balance FROM Accounts WHERE accountNo = 67890 Result: 2846.92

  18. Disadvantages of File Processing Systems • Data Dependence • Data Redundancy (Duplication of data) • Limited Data Sharing • Lengthy Development Times • Excessive Program Maintenance

  19. Advantages of Database Approach • Program-Data Independence: No need to rewrite programs when data is modified • Minimal Data Redundancy • Improved Data Consistency • Improved Data Sharing • Increased Application Development Productivity.

  20. Advantages of Database Approach • Enforcement of Standards • Improved Data Quality (Constraints) • Better Data Accessibility/Responsiveness • Reduced Program Maintenance • Security, Backup/Recovery, Concurrency

  21. Costs and Risks of the Database Approach • New, Specialized Personnel • Installation Management Cost and Complexity • Conversion Costs • Organizational Conflict

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