Database Design - Lecture 1 Database Concepts. 2 Lecture Objectives Data vs Information Historical Roots of Databases What is a database, what it does,

Database Design - Lecture 1

Database Concepts

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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

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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

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Data vs Information

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Data vs Information

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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

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Historical Roots of Databases

Original databases applications: Inventory Control Payroll Banking Reservation Systems

Newer database applications: CAD/CAM GPS systems

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File System Critique

File System Data Management Requires extensive programming in

third-generation language (3GL) Time consuming Makes ad hoc queries impossible Leads to islands of information

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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

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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

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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

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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

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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

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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 better-managed data

Promotes integrated view of organization’s operations

Reduces the probability of inconsistent data

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DBMS Manages Interaction

Figure 1.2

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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)

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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

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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)

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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

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Database vs. File Systems

Figure 1.6

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Database System Environment

Figure 1.7

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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

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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

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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

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Database System Types

Single-user vs. Multiuser Database Single-user desktop Multi-user workgroup Enterprise

Centralized vs. Distributed

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Database Uses

Production or transactional Supports day-to-day operations

Decision support or data warehouse Information for tactical or strategic

decision making Historical Data

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DBMS Functions

Data dictionary management Defines data elements and their

relationships Data storage management

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

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DBMS Functions

Security management Enforces user security and data

privacy within database Multi-user access control

Creates structures that allow multiple users to access the data

Backup and recovery management Provides backup and data recovery

utilities

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DBMS Functions Data integrity management

Promotes and enforces integrity rules to eliminate data integrity problems

Database language and application programming interfaces Provides data access through a query

language Database communication interfaces

Allows database to accept end-user requests within a computer network environment

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Where do we go from here? Data Modeling

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Where do we go from here? Data Modeling