Chapter 1
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File Systems and Databases
Prof. Sin-Min Lee
Dept. of Computer Science
Introducing the Database
Major Database Concepts
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Data
and information
Data - Raw facts
Information - Processed data
Data
management
Database
Metadata
Database
management system (DBMS)
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Sales per Employee for Each of ROBCOR’S Two Divisions
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Figure 1.1
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Introducing the Database
Importance of DBMS
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It helps make data management more efficient
and effective.
Its query language allows quick answers to ad
hoc queries.
It provides end users better access to more and
better-managed data.
It promotes an integrated view of organization’s
operations -- “big picture.”
It reduces the probability of inconsistent data.
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The DBMS Manages the Interaction
Between the End User and the Database
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Figure 1.2
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Introducing the Database
Why Database Design Is Important?
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A well-designed database facilitates data
management and becomes a valuable information
generator.
A poorly designed database is a breeding ground
for uncontrolled data redundancies.
A poorly designed database generates errors that
lead to bad decisions.
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Historical Roots
Why Study File Systems?
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It provides historical perspective.
It teaches lessons to avoid pitfalls of data
management.
Its simple characteristics facilitate understanding
of the design complexity of a database.
It provides useful knowledge for converting a file
system to a database system.
Contents of the CUSTOMER File
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Figure 1.3
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Table 1.1 Basic File Terminology
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Data
“Raw” facts that have little meaning unless they have been
organized in some logical manner. The smallest piece of data
that can be “recognized” by the computer is a single
character, such as the letter A, the number 5, or some
symbol such as; ‘ ? > * +. A single character requires one
byte of computer storage.
Field
A character or group of characters (alphabetic or numeric)
that has a specific meaning. A field might define a telephone
numbers, a birth date, a customer name, a year-to-date
(YTD) sales value, and so on.
Record
A logically connected set of one or more fields that describes
a person, place, or thing. For example, the fields that
comprise a record for a customer named J. D. Rudd might
consist of J. D. Rudd’s name, address, phone number, date
of birth, credit limit, unpaid balance, and so on.
File
A collection of related records. For example, a file might
contain data about ROBCOR Company’s vendors; or, a file
might contain the records for the students currently enrolled
at Gigantic University.
Contents of the AGENT File
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Figure 1.4
A Simple File System
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Figure 1.5
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File System Critique
File System Data Management
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File systems require extensive programming in a
third-generation language (3GL).
As the number of files expands, system
administration becomes difficult.
Making changes in existing file structures is
important and difficult.
Security features to safeguard data are difficult to
program and usually omitted.
Difficulty to pool data creates islands of
information.
File System Critique
Structural and Data Dependence
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Structural Dependence
A change in any file’s structure requires the
modification of all programs using that file.
Data Dependence
A change in any file’s data characteristics requires
changes in all data access programs.
Significance of data dependence is the difference
between the data logical format and the data
physical format.
Data dependence makes file systems extremely
cumbersome from a programming and data
management point of view.
File System Critique
Field Definitions and Naming Conventions
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A good (flexible) record definition anticipates
reporting requirements by breaking up fields into
their components.
Example:
– Customer Name Last Name, First Name, Initial
– Customer Address Street Address, City, State
FIELD
CONTENTS
CUS_LNAME
Customer last name
CUS_FNAME
Customer first name
CUS_INITIAL
Customer initial
CUS_AREACODE
Customer area code
CUS_PHONE
Customer phone
CUS_ADDRESS
Customer street address or box number
CUS_CITY
Customer city
CUS_STATE
Customer state
File System Critique
Field Definitions and Naming Conventions
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Selecting proper field names is very important.
Names must be as descriptive as possible within
restrictions.
Naming must reflect designer’s documentation needs
and user’s reporting and processing requirements.
File System Critique
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Data Redundancy:
Uncontrolled data redundancy sets the
stage for
Data Inconsistency (lack of data integrity)
Data anomalies
Modification anomalies
Insertion anomalies
Deletion anomalies
Figure 1.6
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The Database System Environment
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Figure 1.7
Figure 1.7
Database Systems
The Database System Components
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Hardware
Computer
Peripherals
Software
Operating systems software
DBMS software
Applications programs and utilities software
Database Systems
The Database System Components
People
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Procedures
Systems administrators
Database administrators (DBAs)
Database designers
Systems analysts and programmers
End users
Instructions and rules that govern the design and use of
the database system
Data
Collection of facts stored in the database
Database Systems
The Database System Components
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The complexity of database systems depends on
various organizational factors:
Organization’s size
Organization’s function
Organization’s corporate culture
Organizational activities and environment
Database solutions must be cost effective AND
strategically effective.
Database Systems
Types of Database Systems
Number of Users
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Single-user
– Desktop database
Multiuser
– Workgroup database
– Enterprise database
Scope
Desktop
Workgroup
Enterprise
Database Systems
Types of Database Systems
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Location
Centralized
Distributed
Use
Transactional (Production)
Decision support
Data warehouse
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