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ITM 102 (371)
Lecture

Chapter 6

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Department
Information Technology Management
Course
ITM 102
Professor
Franklyn Prescod
Semester
Fall

Description
Chapter 6 6.1 File organization terms and concepts: • Bit: Smallest unit of data; binary digit (0,1) • Byte: Group of bits that represents a single character • Field: Group of words or a complete number • Record: Group of related fields • File: Group of records of same type • Database: Group of related files • Entity: Person, place, thing, event about which information is maintained • Attribute: Description of a particular entity • Key field: Identifier field used to retrieve, update, sort a record Problems with the Traditional File Environment: • Data Redundancy and Inconsistency: • Data redundancy: The presence of duplicate data in multiple data files so that the same data are stored in more than one place or location • Data inconsistency: The same attribute may have different values. • Program-Data Dependence: • The coupling of data stored in files and the specific programs required to update and maintain those files such that changes in programs require changes to the data • Lack of Flexibility • A traditional file system can deliver routine scheduled reports after extensive programming efforts, but it cannot deliver ad-hoc reports or respond to unanticipated information requirements in a timely fashion • Poor security • Management may have no knowledge of who is accessing or making changes to the organization’s data • Lack of data sharing and availability: • Information cannot flow freely across different functional areas or different parts of the organization. 6.2 The Database Approach to Data Management  A database management system(DBMS) is software that permits an organization to centralize data, manage them efficiently, and provide access to the stored data by application programs. Database management systems How a DBMS solves the problems of the traditional file environment • A DBMS reduces data redundancy and inconsistency by minimizing isolated files in which the same data are repeated. Relational DBMS • Represents data as two-dimensional tables called relations • Relates data across tables based on common data element • Examples: Access, DB2, Oracle, MS SQL Server Operations of a Relational DBMS • Select: Creates subset of rows that meet specific criteria • Join: Combines relational tables to provide users with information • Project: Enables users to create new tables containing only relevant information Object-oriented DBMS • Stores data and procedures as objects that can be retrieved and shared automatically • Provides capabilities of both object-oriented and relational DBMS Hybrid OODBMS: • combine benefits of relational and object-oriented DBMS Capabilities of Database Management Systems Data Definition Language • DBMS capability that specifies the structure and content of the database. Data Dictionary • An automated or manual tool for storing and organizing information about the data maintained in a database Querying and Reporting • Data manipulation language is used to add, change, delete, and retrieve the data in the database. • Structured Query Language or SQL is the standard data manipulation language for relational database management systems. Designing Databases • Conceptual design: Abstract model of database from a business perspective • Physical design: Detailed description of business information needs • Entity-relationship diagram: Methodology for documenting databases illustrating relationships between database entities. • Normalization: Process of creating small stable data structures from complex groups of data Distributed database: • A database that is stored in more than one physical location • Reduce the vulnerability of a single, massive central site • Increase service and responsi
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