ADM 1370 Lecture Notes - Lecture 18: Database, Data Redundancy, Meridian Regional Airport
3 May 2018
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Class 18
Review of Definitions & Concepts: Database & DBMS
• Database
o A collection of data organized to serve many applications efficiently by
centralizing data and controlling redundant and inconsistent data
▪ 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
• The database management system (DBMS)
o A software package to create and maintain databases
o Acts as interface between application programs and physical data files
o Separates logical and physical views of data
Principles of Databases: Data Access Technology Architectures
Principles of Databases: Physical vs Logical Views
• A DBMS separates the logical and the physical view of the data
• Physical view
o How data is organized, specified and sorted
• Logical view
o How data appears to the end user
Example: HR Database and DBMS
Relational DBMS Concepts: Tables, Records & Fields
• Represents data as two-dimensional tables
• Related data across tables based on common data element
• Examples of relational DBMS: access, oracle, DM2, MS SQL server
• A bookstore database with a single file named “books”
• Title and publisher column = attributes (fields)
• ISBM number cell = key field
• Info under ISBM number column = record
Relational DBMS Concepts: Entities, Entity Classes, and Attributes
• Entity
o A person, place, thing, transaction, or event about which information is stored
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