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Chapter 1
Introduction to Database
Concepts
1
Concepts
Database Principles: Fundamentals of Design, Implementation and
Management, Ninth Edition, Rob and Coronel
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In this chapter, you will learn:
� The difference between data and information
� What a database is, what the different types
of databases are, and why they are valuable
assets for decision making
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assets for decision making
� The importance of database design
� How modern databases evolved from file
systems
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In this chapter, you will learn
(continued):
� About flaws in file system data management
� What the database system’s main components are and how a database system differs from a file system
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differs from a file system
� The main functions of a database management system (DBMS)
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Introduction
� Good decisions require good information
derived from raw facts
� Data is managed most efficiently when stored
in a database
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in a database
� Databases evolved from computer file
systems
� Understanding file system characteristics is
important
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Why Databases?
� Databases solve many of the problems
encountered in data management
� Used in almost all modern settings involving data management:
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� Business
� Research
� Administration
� Important to understand how databases work
and interact with other applications
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Data vs. Information
� Data are raw facts, unprocessed information
� Information is the result of processing raw
data to reveal meaning
� Information requires context to reveal
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� Information requires context to reveal
meaning
� Raw data must be formatted for storage,
processing, and presentation
� Data are the foundation of information
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Data vs. Information (cont’d.)
� Data: building blocks of information
� Information produced by processing data
� Information used to reveal meaning in data
Accurate, relevant, timely information is the
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� Accurate, relevant, timely information is the
key to good decision making
� Good decision making is the key to
organizational survival
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Transforming Raw Data into
Information
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Transforming Raw Data into
Information (continued)
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Transforming Raw Data into
Information (continued)
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Transforming Raw Data into
Information (continued)
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Introducing the Database
� Data Management is a discipline that focuses
on the proper generation, storage and retrieval
of data.
� Database: shared, integrated computer
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structure that stores a collection of:
� End-user data: raw facts of interest to end user
� Metadata: data about data
� Provides description of data characteristics and
relationships in data
� Complements and expands value of data
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Introducing the Database and the
DBMS (continued)� DBMS (database management system):
� Collection of programs that manages database structure and controls access to data
� Possible to share data among multiple
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Possible to share data among multiple applications or users
� Makes data management more efficient and effective
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Role and Advantages of the DBMS
� DBMS is the intermediary between the user and
the database
� Database structure stored as file collection
� Can only access files through the DBMS
� DBMS enables data to be shared
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� DBMS integrates many users’ views of the data
� End users have better access to more and
better-managed data
� Promotes integrated view of organization’s operations
� Probability of data inconsistency is greatly reduced
� Possible to produce quick answers to ad hoc queries
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Role and Advantages of the DBMS
(cont’d.)� Advantages of a DBMS:
� Improved data sharing
� Improved data security
� Better data integration
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� Better data integration
� Minimized data inconsistency
� Improved data access
� Improved decision making
� Increased end-user productivity
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Role and Advantages of the DBMS
(continued)
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Types of Databases
� Databases can be classified according to:
� Number of users
� Database location(s)
� Expected type and extent of use
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Expected type and extent of use
� Single-user database supports only one
user at a time
� Desktop database: single-user; runs on PC
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Types of Databases (continued)
� Multiuser database supports multiple users
at the same time
� Workgroup and enterprise databases
� Workgroup:
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� Workgroup:
� Multi-user database that supports a small group of users
or a single department
� Enterprise:
� Multi-user database that supports a large group of users
or an entire organization
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Types of Databases (continued)
Can be classified by location:
� Centralized:
� Supports data located at a single site
� Distributed:
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� Distributed:
� Supports data distributed across several sites
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Types of Databases (continued)
Can be classified by use:
� Transactional (or production):
� Supports a company’s day-to-day operations
� Data warehouse:
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Data warehouse:
� Stores data used to generate information required to make tactical or strategic decisions
� Often used to store historical data
� Structure is quite different
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Types of Databases (cont'd.)
� Unstructured data exist in their original
(raw)state – unable to be processed
� Structured data result from formatting
� Structure applied based on type of processing to be performed – generate information
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be performed – generate information
� Semistructured data have been processed
to some extent – e.g. webpage, email etc
� Extensible Markup Language (XML) represents data elements in textual format
� XML database supports semistructured XML data
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Why Database Design Is Important
� Database design focuses on design of
database structure used for end-user data
� Designer must identify database’s expected use
� Well-designed database:
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� Well-designed database:
� Facilitates data management
� Generates accurate and valuable information
� Poorly designed database:
� Causes difficult-to-trace errors
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Evolution of File System Data
Processing� Reasons for studying file systems:
� Complexity of database design is easier to understand
� Understanding file system problems helps to avoid
problems with DBMS systems
Knowledge of file system is useful for converting file
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� Knowledge of file system is useful for converting file
system to database system
� File systems typically composed of collection of
file folders, each tagged and kept in cabinet
� Organized by expected use
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Evolution of File System Data
Processing (cont'd.)
� Contents of each file folder are logically related
� Manual systems
� Served as a data repository for small data collections
� Collection of file folders kept in file cabinet
Organization within folders based on data’s expected use
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� Organization within folders based on data’s expected use (ideally logically related)
� System adequate for small amounts of data with few reporting requirements
� Finding and using data in growing collections of file folders became time-consuming and cumbersome
� Designed the application programs
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Evolution of File System Data
Processing (cont'd.)
� Initially, computer file systems
resembled manual systems
� Computerized file systems
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Computerized file systems
� Data processing (DP) specialist converted
computer file structure from manual system
� Wrote software that managed the data
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Historical Roots: Files and File Systems
(continued)
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Historical Roots: Files and File
Systems (continued)
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Historical Roots: Files and File Systems
(continued)
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Historical Roots: Files and File
Systems (continued)
� As number of databases increased, small file
system evolved
� Each file used its own application programs
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� Each file was owned by individual or
department who commissioned its creation
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Historical Roots: Files and File Systems
(continued)
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Problems with File System
Data Management� Every task requires extensive programming in a
third-generation language (3GL)
� Programmer must specify task and how it must be done
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� Modern databases use fourth-generation
languages (4GL)
� Allow users to specify what must be done without specifying how it is to be done
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Problems with File System
Data Management
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Problems with File System Data
Processing� File systems were an improvement over manual
system
� File systems used for more than two decades
� Understanding the shortcomings of file systems aids in
development of modern databases
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development of modern databases
� Many problems not unique to file systems
� Even simple file system retrieval task required
extensive programming
� Ad hoc queries impossible
� Changing existing structure difficult
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Problems with File System Data
Processing (cont'd.)� Security features difficult to program
� Often omitted in file system environments
� Summary of file system limitations:
� Requires extensive programming
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� Requires extensive programming
� Cannot perform ad hoc queries
� System administration is complex and difficult
� Difficult to make changes to existing structures
� Security features are likely to be inadequate
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Structural and Data Dependence
� Structural dependence: access to a file is
dependent on its own structure
� All file system programs must be modified to conform to a new file structure
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� Structural independence: change file
structure without affecting data access
� Data dependence: data access changes
when data storage characteristics change
� Data independence: data storage
characteristics do not affect data access38
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Problems with File System
Data Management� Time-consuming, high-level activity
� As number of files expands, system
administration becomes difficult
� Making changes in existing file structure is
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� Making changes in existing file structure is
difficult
� File structure changes require modifications
in all programs that use data in that file
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Data Redundancy
� File system structure makes it difficult to
combine data from multiple sources
� Vulnerable to security breaches
� Organizational structure promotes storage of
same data in different locations
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same data in different locations
� Islands of information
� Data stored in different locations is unlikely
to be updated consistently
� Data redundancy: same data stored
unnecessarily in different places
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Data Redundancy (cont'd.)
� Data inconsistency: different and conflicting
versions of same data occur at different
places
� Data anomalies: abnormalities when all
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� Data anomalies: abnormalities when all
changes in redundant data are not made
correctly
� Update anomalies
� Insertion anomalies
� Deletion anomalies
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Data Redundancy
Types of data anomalies:
� Update anomalies
� Occur when changes must be made to existing records
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records
� Insertion anomalies
� Occur when entering new records
� Deletion anomalies
� Occur when deleting records
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Database Systems
� Problems inherent in file systems make using
a database system desirable
� File system
� Many separate and unrelated files
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� Many separate and unrelated files
� Database
� Logically related data stored in a single logical data repository
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Database Systems
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The Database System Environment
� Database system: defines and regulates the collection,
storage, management, use of data
� Database system is composed of five main parts:
� Hardware
� Software
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� People
� Procedures
� Data
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The Database System Environment
(continued)
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The Database System Environment
(cont'd.)� Hardware: all the system’s physical devices
� Software: three types of software required:
� Operating system software
� DBMS software
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� DBMS software
� Application programs and utility software
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The Database System Environment
(cont'd.)� People: all users of the database system
� System and database administrators
� Database designers
� Systems analysts and programmers
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� Systems analysts and programmers
� End users
� Procedures: instructions and rules that
govern the design and use of the database
system
� Data: the collection of facts stored in the
database48 Database Systems, 9th Edition
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DBMS Functions
� DBMS performs functions that guarantee
integrity and consistency of data
� Data dictionary management
� defines data elements and their relationships
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� Data storage management
� stores data and related data entry forms, report
definitions, etc.
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5050 Database Systems, 9th Edition
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5151 Database Systems, 9th Edition
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DBMS Functions (continued)
� Data transformation and presentation
� translates logical requests into commands to
physically locate and retrieve the requested data
� Security management
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� enforces user security and data privacy within
database
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DBMS Functions (continued)
� Multi-user access control
� uses sophisticated algorithms to ensure multiple
users can access the database concurrently
without compromising the integrity of the
database
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database
� Backup and recovery management
� provides backup and data recovery procedures
� Critical to preserving database’s integrity
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DBMS Functions (continued)
� Data integrity management
� promotes and enforces integrity rules� Minimizes redundancy
� Maximizes consistency
Database access languages and application
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� Database access languages and application programming interfaces
� provide data access through a query language
� Database communication interfaces
� allow database to accept end-user requests via
multiple, different network environments
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DBMS Functions (continued)
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DBMS Functions (continued)
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Managing the Database System:
A Shift in Focus� Database system provides a framework in which
strict procedures and standards enforced
� Role of human changes from programming to
managing organization’s resources
Database system enables more sophisticated
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� Database system enables more sophisticated
use of the data
� Data structures created within the database and
their relationships determine effectiveness
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Managing the Database System:
A Shift in Focus (cont'd.)� Disadvantages of database systems:
� Increased costs
� Management complexity
� Maintaining currency
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� Maintaining currency
� Vendor dependence
� Frequent upgrade/replacement cycles
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Summary
� Data are raw facts
� Information is the result of processing data to
reveal its meaning
� Accurate, relevant, and timely information is
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� Accurate, relevant, and timely information is
the key to good decision making
� Data are usually stored in a database
� DBMS implements a database and manages
its contents
60 Database Systems, 9th Edition
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Summary (cont'd.)
� Metadata is data about data
� Database design defines the database
structure
� Well-designed database facilitates data
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� Well-designed database facilitates data management and generates valuable information
� Poorly designed database leads to bad decision making and organizational failure
� Databases evolved from manual and
computerized file systems
61 Database Systems, 9th Edition
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Summary (cont'd.)
� In a file system, data stored in independent
files
� Each requires its own management program
� Some limitations of file system data
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� Some limitations of file system data
management:
� Requires extensive programming
� System administration is complex and difficult
� Changing existing structures is difficult
� Security features are likely inadequate
� Independent files tend to contain redundant data
� Structural and data dependency problems62 Database Systems, 9th Edition
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Summary (cont'd.)
� Database management systems were
developed to address file system’s inherent
weaknesses
� DBMS present database to end user as
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� DBMS present database to end user as
single repository
� Promotes data sharing
� Eliminates islands of information
� DBMS enforces data integrity, eliminates
redundancy, and promotes security
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The End
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The End