ITIS 1P97 Lecture Notes - Lecture 7: Data Definition Language, Data Redundancy, Unique Key

• School: Brock University
• Department: Information Technology Information Systems
• Course: ITIS 1P97
• Professor: Sara Cumming

Document Summary

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. Poor security: management may have no knowledge of who is accessing or making changes to the organization"s data. Lack of data sharing: information cannot flow freely across different functional areas. Relational dbms: represents data as two-dimensional tables called relations. Data definition language: specifies structure of the database. Data dictionary: stores definition of data elements and their characteristics. Conceptual design: abstract model of database from a business perspective. Physical design: detailed description of business information needs. Entity-relationship diagram: illustrating relationships between database entities. Normalization: process of creating small stable data structure from groups of data.