Download Data

Database Design - Lecture 1
Database Concepts
Lecture Objectives




Data vs Information
Historical Roots of Databases
What is a database, what it does, and why
database design is important
What a DBMS is, what it does, and how it fits
into the database system
2
Data vs Information

Information System



Encompasses logic, algorithms and data
Transformation of data into useful information
Data versus Information




Data constitute building blocks of information
Information produced by processing data
Good, timely, relevant information key to decision
making
Good decision making key to organization’s
survival
3
Data vs Information
4
Data vs Information
5
Historical Roots of Databases


First applications focused on clerical tasks
File systems developed to address needs



Data organized according to expected use
Data Processing (DP) specialists computerized
manual file systems
Requests for information quickly followed


Large amounts of data
Many users require simultaneous access
6
Historical Roots of Databases

Original databases applications:





Inventory Control
Payroll
Banking
Reservation Systems
Newer database applications:


CAD/CAM
GPS systems
7
File System Critique

File System Data Management




Requires extensive programming in thirdgeneration language (3GL)
Time consuming
Makes ad hoc queries impossible
Leads to islands of information
8
File System Critique (con’t.)

Data Dependence




Change in file’s data characteristics requires
modification of data access programs
Must tell program what to do and how
Makes file systems cumbersome from
programming and data management views
Structural Dependence

Change in file structure requires modification of
related programs
9
File System Critique (con’t.)

Field Definitions and Naming Conventions




Flexible record definition anticipates reporting
requirements
Selection of proper field names important
Attention to length of field names
Use of unique record identifiers
10
File System Critique (con’t.)

Data Redundancy


Different and conflicting versions of same data
Results of uncontrolled data redundancy

Data anomalies




Modification
Insertion
Deletion
Data inconsistency

Lack of data integrity
11
Introducing the Database


Data is stored in a database and must be
structured and arranged for storage,
extraction and processing
Database consists of a collection of logically
related data stored in a single repository
which consists of end user data and metadata
12
Database Management


A Database Management System (DBMS)
manages the access to the database (and
ultimately the data)
Database Management System (DBMS):
 Collection of programs that manages
database structure and controls access to
data
 Sharing of data among multiple
applications and users
13
Importance of DBMS
 Makes data management more efficient
and effective
 Query language allows quick answers to ad
hoc queries
 Provides better access to more and bettermanaged data
 Promotes integrated view of organization’s
operations
 Reduces the probability of inconsistent
data
14
DBMS Manages Interaction
Figure 1.2
15
Importance of a DBMS

For Top Management



Provides the information necessary for
strategic decision making and strategic
planning
Provides access to external and internal
data
Provides information on company
performance and whether they are
achieving their goals (targets)
16
Importance of a DBMS

For Middle Management


Provides data necessary for tactical
decisions and planning
Provides a framework for enforcing and
ensuring the security and privacy of the
data
17
Importance of a DBMS

For Operational Management



Provides timely information for customer
support
Produce query results within specified
performance levels
Represents and supports the company
operations as closely as possible
(operational data)
18
Database Design

Importance of Good Design



eliminates data redundancy
eliminates errors leading to bad decisions
Practical Approach


Focus on principles and concepts of database
design
Importance of logical design
19
Database vs. File Systems
Figure 1.6
20
Database System Environment
Figure 1.7
21
DBMS environment roles

Database Administrators

Responsible for:





Physical implementation of the DBMS
Security and integrity control of the DBMS
Maintenance of the operational system
Ensuring satisfactory performance of the
applications for users
Requires detailed knowledge of the
target DBMS and the system
environment
22
DBMS environment roles

Database Designer

Logical Database Designer

Responsible for:




Identifying the data (entities and attributes)
Identifying the relationships between the
data
Identifying the constraints on the data
Ensures that the direction of database
development ultimately supports corporate
objectives
23
DBMS environment roles

Database Designer

Physical Database Designer


Decides how the logical database design is
to be physically realized
Responsible for:



Mapping the logical database design into a
set of tables and integrity constraints
Selecting specific storage structures and
access methods for the data to achieve good
performance
Designing any security measures required on
the data
24
Database System Types

Single-user vs. Multiuser Database




Single-user desktop
Multi-user workgroup
Enterprise
Centralized vs. Distributed
25
Database Uses

Production or transactional


Supports day-to-day operations
Decision support or data warehouse


Information for tactical or strategic
decision making
Historical Data
26
DBMS Functions

Data dictionary management


Data storage management


Defines data elements and their
relationships
Stores data and related data entry forms,
report definitions, etc
Data transformation and presentation

Translates logical requests into commands
to physically locate and retrieve the
requested data
27
DBMS Functions

Security management


Multi-user access control


Enforces user security and data privacy
within database
Creates structures that allow multiple
users to access the data
Backup and recovery management

Provides backup and data recovery utilities
28
DBMS Functions

Data integrity management


Database language and application
programming interfaces


Promotes and enforces integrity rules to
eliminate data integrity problems
Provides data access through a query
language
Database communication interfaces

Allows database to accept end-user
requests within a computer network
environment
29
Where do we go from here?

Data Modeling
30
Where do we go from here?

Data Modeling
31