Organizing Data Chapter 5

Data Hierachy

Table = Entities X Attributes Entities = Records Attributes = Fields

Files vs. Databases In the 70’s and early 80’s Information Systems used files to store data “Traditional Approach” In the mid-80’s “The Database Approach” became the standard Traditional Appoach –Data redundancy –Application dependent on data format and vice versa.

Traditional Approach

Database Approach MIS DBMS

Hierarchical Models

(E-R) Entity-Relatonship Diagrams

Network Model

Relational Model Find the name and hire date of the manager working on the sales manual project

Schemas Schema - A description of the database Subschema – describes a subset of the database and which users have access to this subset

Data Definition Language Defines the data in a Database Describes relationships between different data Provides a Logical view of the data Used to describe Schemas and Subschemas

Data Dictionary Entry A more detailed description of the data in a database Specifies data types and ranges Assists programmers in understanding the data

Logical vs. Physical Access Paths Database Management Systems concentrate on Physical access to the underlying tables –Concurrency control –Query’s –Creating/deleting tables MIS systems are often software packages that (Logically) interface with a DBMS –monthly reports –charts –automated inquiries