Download Databases

Mgt 20600:
IT Management & Applications
Databases
Tuesday
April 4, 2006
Reminders

Reading
– For today
 Fundamentals text, Chapter Three, Organizing Data
and Information
– For next class on April 11th



Fundamentals text, Chapter Six, Information and Decision
Support Systems
Homework
– Homework Four
 Databases
 Due Thursday, April 14th
Next week: Decision Support Systems
Databases
A well-designed and well-managed
database is an extremely valuable tool in
supporting decision making
 Databases are key corporate assets
 Databases are the foundation for
sophisticated analyses that provide
business intelligence

– What new products to design
– How to market to particular customer groups
– Which customer groups are the most profitable
Traditional Approach
to Data Management
Traditional
approach: separate
data files are
created for each
application
Results in data
redundancy
(duplication)
Data
redundancy
conflicts with
data integrity
Database Approach
to Data Management
Database approach:
pool of related data is
shared by multiple
applications
Significant
advantages over
traditional
approach
Advantages of Database Approach
Improved strategic use of data
 Reduced data redundancy
 Improved data integrity
 Easier modification and updating
 Data and program independence
 Better access to data and information
 Standardization of data access
 A framework for program development
 Better overall protection of the data
 Shared data and information resources

Disadvantages of the
Database Approach
 More
complexity
 More difficult to recover from a
failure
 More expensive
Databases
 Databases
must contain
– Accurate information
– Right kinds of information
– Current information
– Information from all organizational
functions
Database Data

Data regarding
– Important entities
 Customers
 Suppliers
 Transactions
– Each entity will have a number of attributes
about which you want to collect and store
information
 Customer
address
 Customer phone number
 Customer account number
Entities, Attributes, Keys
Entity: a generalized class of people,
places, or things (objects) for which
data is collected, stored, and
maintained (Table and records)
Attribute: a characteristic of an
entity (fields)
Data item: a value of an attribute
(fields)
Key: field(s) that identify a record
Primary key: field(s) that uniquely
identify a record
Hierarchy of Data
Field: name, number, or
characters that describe
an aspect of a business
object or activity
Record: a collection of
related data fields
File: a collection of
related records
Database: a collection of
integrated and related
files
Data Modeling and the
Relational Database Model
 When
building a database, consider:
– Content: What data should be collected,
at what cost?
– Access: What data should be provided
to which users, and when?
– Logical structure: How should data be
arranged to make sense to a given
user?
– Physical organization: Where should
data be physically located?
Data Modeling
 Building
a database requires two
types of design
– Logical design
 Shows
an abstract model of how data
should be structured and arranged to meet
an organization’s information needs
– Physical design
 Fine-tunes
the logical database design for
performance and cost considerations
Data Modeling
 Data
model: a diagram of data
entities and their relationships
 Entity-relationship (ER)
diagrams: data models that use
basic graphical symbols to show the
organization of and relationships
between data
Data Modeling
An Entity-Relationship (ER) Diagram for a
Customer Order Database
The Relational Database Model
Relational model: all data elements are
placed in two-dimensional tables
(relations), which are the logical
equivalent of files
 In the relational model:

– Each table represents a data entity
– Each row of a table represents a specific
instance of a data entity
– Columns of the table represent attributes
The Relational Database Model
A Relational Database Model
Creating and Modifying the
Database
 Data
definition language (DDL)
– Collection of instructions/commands that
define and describe data and data relationships
in a database
– Allows database creator to describe the data
and the data relationships that are to be
contained in the schema and the subschemas
 Data
dictionary:
a detailed description of
all the data used in the database
Storing and Retrieving Data
Logical and Physical Access Paths
Providing a User View
 Schema:
description of the entire
database
 User view: user-accessible portion
of the database
 Subschema
– Contains a description of a subset of the
database
– Identifies which users can view and
modify the data items in the subset
– Is used to create different user views
Providing a User View
The Use of Schemas and Subschemas
Creating and Modifying
the Database
A Typical Data Dictionary Entry
Manipulating Data and
Generating Reports

Data manipulation language (DML):
commands that manipulate the data in a
database
– Query-By-Example (QBE): a visual approach
to developing database queries or requests
– Structured Query Language (SQL): ANSI
standard query language for relational
databases
– Database programs can produce reports,
documents, and other outputs
Manipulating Data
 Selecting:
eliminates rows
according to criteria
 Projecting: eliminates columns in a
table
 Joining: combines two or more
tables
 Linking: relates or links two or more
tables using common data attributes
Manipulating Data
Linking Data Tables to Answer an Inquiry
Database Administration
 Database
administrator (DBA):
directs or performs all activities to
maintain a database environment
– Designing, implementing, and
maintaining the database system and
the DBMS
– Establishing policies and procedures
– Training employees
Selecting a Database
Management System
 Important
characteristics of
databases to consider:
– Size of the database
– Number of concurrent users
– Performance
– Ability to be integrated with other
systems
– Features of the DBMS
– Vendor considerations
– Cost of the system