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Database Overview - software engineering
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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
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
22
assets for decision making
� The importance of database design
� How modern databases evolved from file
systems
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
33
differs from a file system
� The main functions of a database management system (DBMS)
Introduction
� Good decisions require good information
derived from raw facts
� Data is managed most efficiently when stored
in a database
4
in a database
� Databases evolved from computer file
systems
� Understanding file system characteristics is
important
Why Databases?
� Databases solve many of the problems
encountered in data management
� Used in almost all modern settings involving data management:
5
� Business
� Research
� Administration
� Important to understand how databases work
and interact with other applications
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
6
� Information requires context to reveal
meaning
� Raw data must be formatted for storage,
processing, and presentation
� Data are the foundation of information
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
7
� Accurate, relevant, timely information is the
key to good decision making
� Good decision making is the key to
organizational survival
Transforming Raw Data into
Information
88
Transforming Raw Data into
Information (continued)
99
Transforming Raw Data into
Information (continued)
1010
Transforming Raw Data into
Information (continued)
1111
Introducing the Database
� Data Management is a discipline that focuses
on the proper generation, storage and retrieval
of data.
� Database: shared, integrated computer
12
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
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
1313
Possible to share data among multiple applications or users
� Makes data management more efficient and effective
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
1414
� 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
Role and Advantages of the DBMS
(cont’d.)� Advantages of a DBMS:
� Improved data sharing
� Improved data security
� Better data integration
15
� Better data integration
� Minimized data inconsistency
� Improved data access
� Improved decision making
� Increased end-user productivity
15
Role and Advantages of the DBMS
(continued)
1616
Types of Databases
� Databases can be classified according to:
� Number of users
� Database location(s)
� Expected type and extent of use
17
Expected type and extent of use
� Single-user database supports only one
user at a time
� Desktop database: single-user; runs on PC
Types of Databases (continued)
� Multiuser database supports multiple users
at the same time
� Workgroup and enterprise databases
� Workgroup:
1818
� 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
Types of Databases (continued)
Can be classified by location:
� Centralized:
� Supports data located at a single site
� Distributed:
1919
� Distributed:
� Supports data distributed across several sites
Types of Databases (continued)
Can be classified by use:
� Transactional (or production):
� Supports a company’s day-to-day operations
� Data warehouse:
2020
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
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
21
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
22
2323
2424
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:
25
� Well-designed database:
� Facilitates data management
� Generates accurate and valuable information
� Poorly designed database:
� Causes difficult-to-trace errors
25
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
26
� 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
26
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
27
� 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
27
Evolution of File System Data
Processing (cont'd.)
� Initially, computer file systems
resembled manual systems
� Computerized file systems
28
Computerized file systems
� Data processing (DP) specialist converted
computer file structure from manual system
� Wrote software that managed the data
28
Historical Roots: Files and File Systems
(continued)
2929
Historical Roots: Files and File
Systems (continued)
3030
Historical Roots: Files and File Systems
(continued)
3131
Historical Roots: Files and File
Systems (continued)
� As number of databases increased, small file
system evolved
� Each file used its own application programs
3232
� Each file was owned by individual or
department who commissioned its creation
Historical Roots: Files and File Systems
(continued)
3333
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
3434
� Modern databases use fourth-generation
languages (4GL)
� Allow users to specify what must be done without specifying how it is to be done
Problems with File System
Data Management
3535
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
36
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
36
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
37
� 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
37
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
38
� 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
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
3939
� Making changes in existing file structure is
difficult
� File structure changes require modifications
in all programs that use data in that file
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
40
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
40
Data Redundancy (cont'd.)
� Data inconsistency: different and conflicting
versions of same data occur at different
places
� Data anomalies: abnormalities when all
41
� Data anomalies: abnormalities when all
changes in redundant data are not made
correctly
� Update anomalies
� Insertion anomalies
� Deletion anomalies
41
Data Redundancy
Types of data anomalies:
� Update anomalies
� Occur when changes must be made to existing records
4242
records
� Insertion anomalies
� Occur when entering new records
� Deletion anomalies
� Occur when deleting records
Database Systems
� Problems inherent in file systems make using
a database system desirable
� File system
� Many separate and unrelated files
4343
� Many separate and unrelated files
� Database
� Logically related data stored in a single logical data repository
Database Systems
4444
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
4545
� People
� Procedures
� Data
The Database System Environment
(continued)
4646
The Database System Environment
(cont'd.)� Hardware: all the system’s physical devices
� Software: three types of software required:
� Operating system software
� DBMS software
47
� DBMS software
� Application programs and utility software
47 Database Systems, 9th Edition
The Database System Environment
(cont'd.)� People: all users of the database system
� System and database administrators
� Database designers
� Systems analysts and programmers
48
� 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
DBMS Functions
� DBMS performs functions that guarantee
integrity and consistency of data
� Data dictionary management
� defines data elements and their relationships
4949
� Data storage management
� stores data and related data entry forms, report
definitions, etc.
5050 Database Systems, 9th Edition
5151 Database Systems, 9th Edition
DBMS Functions (continued)
� Data transformation and presentation
� translates logical requests into commands to
physically locate and retrieve the requested data
� Security management
5252
� enforces user security and data privacy within
database
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
5353
database
� Backup and recovery management
� provides backup and data recovery procedures
� Critical to preserving database’s integrity
DBMS Functions (continued)
� Data integrity management
� promotes and enforces integrity rules� Minimizes redundancy
� Maximizes consistency
Database access languages and application
5454
� 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
DBMS Functions (continued)
5555
5656
DBMS Functions (continued)
5757
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
58
� Database system enables more sophisticated
use of the data
� Data structures created within the database and
their relationships determine effectiveness
58 Database Systems, 9th Edition
Managing the Database System:
A Shift in Focus (cont'd.)� Disadvantages of database systems:
� Increased costs
� Management complexity
� Maintaining currency
59
� Maintaining currency
� Vendor dependence
� Frequent upgrade/replacement cycles
59 Database Systems, 9th Edition
Summary
� Data are raw facts
� Information is the result of processing data to
reveal its meaning
� Accurate, relevant, and timely information is
60
� 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
Summary (cont'd.)
� Metadata is data about data
� Database design defines the database
structure
� Well-designed database facilitates data
61
� 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
Summary (cont'd.)
� In a file system, data stored in independent
files
� Each requires its own management program
� Some limitations of file system data
62
� 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
Summary (cont'd.)
� Database management systems were
developed to address file system’s inherent
weaknesses
� DBMS present database to end user as
63
� 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
63 Database Systems, 9th Edition
The End
64
The End