Database Systems

Database

– Organized collection of data

Database management system

– Group of programs that manipulate the database

– Provide an interface between the database and its users and other application programs

Database administrator

Skilled IS professional who directs all activities related to an organization’s database

Bit

Circuit that is either on or off

Byte

Typically made up of eight bits

Character

Basic building block of information

Fields

Name, number, or combination of characters that describes an aspect of a business object or activity

Record

Collection of related data fields

File

Collection of related records

Database

– Collection of integrated and related files

Entity

General class of people, places, or things (objects) for which data is collected, stored, and maintained

Attribute

– Characteristic of an entity

Data item

Specific value of an attribute

Key

Field or set of fields in a record that is used to identify the record

Primary key

Field or set of fields that uniquely identifies the record

Foreign key

Refers to the primary key in another table.

Content

Access

Logical structure

Physical organization

When building a database, an organization must consider:

Logical Design
Physical Design

Building a database requires two types of designs:

Logical design

Abstract model of how data should be structured and arranged to meet an organization’s information needs

Physical design

Starts from the logical database design and finetunes it for performance and cost considerations

Enterprise data modeling

Starts by investigating the general data and information needs of the organization at the strategic level

Entity-relationship Diagram

Data models that use basic graphical

symbols to show the organization of and relationships between data

Selecting

Eliminates rows according to certain criteria

Projecting

Eliminates columns in a table

Joining

Combines two or more tables

Linking

Manipulating two or more tables that share at least one common data attribute

Flat file

Simple database program whose records have no

relationship to one another

Single user

Only one person can use the database at a time

– Examples: Access, FileMaker Pro, and InfoPath

Multiple users

– Allow dozens or hundreds of people to access the

same database system at the same time

– Examples: Oracle, Sybase, and IBM

Schema

– Used to describe the entire database

– Can be part of the database or a separate schema

file

DBMS

Can reference a schema to find where to access the

requested data in relation to another piece of data

Concurrency control

– Method of dealing with a situation in which two or more users or applications need to access the same record at the same time

DBA

– Works with users to decide the content of the database

– Works with programmers as they build applications to ensure that their programs comply with database management system standards and conventions

Data administrator

Responsible for defining and implementing consistent principles for a variety of data issues

Front-end

applications interact directly with people

Back-end

applications interact with other programs or applications