Download Communications and Networks Fundamentals

CSBP430 – Database Systems
Chapter 1: Databases and Database
Users
Mamoun Awad
College of Information Technology
United Arab Emirates University
[email protected]
1
In this chapter, you will learn:
Basic Definitions
Example of a Database
Main Characteristics of Database Technology
Additional Benefits of Database Technology
When Not to Use a DBMS
2
Basic Definitions
Database: A collection of related data.
Data: Known facts that can be recorded and have an implicit
meaning.
Mini-world: Some part of the real world about which data is stored
in a database. For example, student grades and transcripts at a
university.
Database Management System (DBMS): A software
package/system to facilitate the creation and maintenance of a
computerized database.
Database System: The DBMS software together with the data itself.
Sometimes, the applications are also included.
3
File Terminology
Data: Raw Facts
Field: Group of characters with specific meaning
Record: Logically connected fields that describe a person,
place, or thing
File: Collection of related records
4
Simple File System
5
File System Critique
File System Data Management
Requires extensive programming
generation language (3GL)
Time consuming
Makes ad hoc queries impossible
Leads to islands of information
in
third-
6
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
7
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
8
Database Systems
Database consists of logically related data stored
in a single repository
Provides
advantages
management approach
over
file
system
Eliminates inconsistency, data anomalies, data
dependency, and structural dependency problems
Stores data structures, relationships, and access paths
9
Database vs. File Systems
10
Database System Environment
11
Example of a Database
(with a Conceptual Data Model)
Mini-world for the example: Part of a UNIVERSITY environment.
Some mini-world entities:
- STUDENTs
- COURSEs
- SECTIONs (of COURSEs)
- (academic) DEPARTMENTs
- INSTRUCTORs
Some mini-world relationships:
- SECTIONs are of specific COURSEs
- STUDENTs take SECTIONs
- COURSEs have prerequisite COURSEs
- INSTRUCTORs teach SECTIONs
- COURSEs are offered by DEPARTMENTs
- STUDENTs major in DEPARTMENTs
12
13
14
Main Characteristics of Database Technology
Self-contained nature of a database system:
A DBMS catalog stores the description of the database. The description is called
meta-data). This allows the DBMS software to work with different databases.
Insulation between programs and data:
Called program-data independence. Allows changing data storage structures
and operations without having to change the DBMS access programs.
Data Abstraction:
A data model is used to hide storage details and present the users with a
conceptual view of the database.
Support of multiple views of the data:
Each user may see a different view of the database, which describes only the
data of interest to that user.
15
16
Additional Benefits of Database Technology
Controlling redundancy in data storage and in development and maintenance efforts.
Sharing of data among multiple users.
Restricting unauthorized access to data.
Providing multiple interfaces to different classes of users.
Representing complex relationships among data.
Enforcing integrity constraints on the database.
Providing backup and recovery services.
Potential for enforcing standards.
Flexibility to change data structures.
Reduced application development time.
Availability of up-to-date information.
Economies of scale.
17
18
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
19
DBMS Manages Interaction
20
Database Design
Importance of Good Design
Poor design results in unwanted data redundancy
Poor design generates errors leading to bad decisions
Practical Approach
Focus on principles and concepts of database design
Importance of logical design
21
Database Models and the Internet
Characteristics of “Internet age” databases
Flexible, efficient, and secure Internet access
Easily used, developed, and supported
Supports complex data types and relationships
Seamless interfaces with multiple data sources and structures
Simplicity of conceptual database model
Many database design,
development tools
implementation,
and
application
Powerful DBMS GUI make DBA job easier
22
When not to use a DBMS
Main inhibitors (costs) of using a DBMS:
High initial investment and possible need for additional hardware.
Overhead for providing generality, security, recovery, integrity, and concurrency
control.
When a DBMS may be unnecessary:
If the database and applications are simple, well defined, and not expected to
change.
If there are stringent real-time requirements that may not be met because of
DBMS overhead.
If access to data by multiple users is not required.
When no DBMS may suffice:
If the database system is not able to handle the complexity of data because of
modeling limitations
If the database users need special operations not supported by the DBMS.
23