ITM 100 Lecture Notes - Lecture 6: Data Redundancy, Unique Key, Sql

• School: Ryerson University
• Department: Information Technology Management
• Course: ITM 100
• Professor: Abbas Kermanti

Document Summary

An organized collection of data stored centrally to serve various information system applications. 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. File: group of records of same type. Field: group of characters as words or numbers. Byte: group of bits that represents a single character. Bit: smallest unit of data; binary digit. Files maintained separately by different departments: each management level could have their own databases. 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 data require changes to the program.