Post on 27-Dec-2015
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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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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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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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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