Feb 26,2008 Fatimah Alakeel 1 Database Design Chapter-1- Basic Concepts Reference: Prof. Mona Mursi Lecture notes Dr.Lilac Safadi Lecture notes
Jan 03, 2016
Feb 26,2008 Fatimah Alakeel 1
Database Design
Chapter-1- Basic ConceptsReference:
Prof. Mona Mursi Lecture notes
Dr.Lilac Safadi Lecture notes
Feb 26,2008 Fatimah Alakeel 2
Database ConceptsDatabase ConceptsData is a meaningless static value. What does 3421 means?
Information is the data you process in a manner that makes it meaningful. Information can be provided only if proper data exists.
A database (DB) is a collection of related persistent data. Can be generated & maintained manually or automatically
Data is what you store in database. Information is what you retrieve from a database.
A database application is a collection of data and the programs that allow the manipulation of these data to meet the information needs of an enterprise
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Database Application: Database Application: ExamplesExamples
KSU Library
Saudia Airline Reservations
Car rental DB
A DB for all schools in Riyadh
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Database Properties Represents the real world (miniworld, Universe of Discourse UoD) Logically coherent collection of data. Designed, built, populated with data for a specific purpose. It has an
intended group of users and their applications. Can be of any size and any degree of complexity. Can be generated and maintained manually or using a computer.
A computerized DB can be created by: A Group of application programs Or by Database Management System (DBMS)
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The Data in the DB are
Shared by multiple users Stored less redundantly Made independent of applications Organized
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Database Management System (DBMS) A collection of programs that enables the users to create and
maintain a database. A general- purpose software system that facilitates the process of :
Defining (specifying data types, structures and constraints) Constructing (storing the data on a storage medium controlled
by DBMS) Manipulating (querying, update, generate reports) And Maintaining
The database for various applications .
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DBS EnvironmentDBS Environment
DatabaseMeta-Data
Data Access
Query Process
Application Programs
DBMS
DBS
Database System = Database + DBMS
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DBMS Capabilities & Responsibilities
1. Control redundancy.
2. Access a large amount of data efficiently.
3. Support a data model in which is conceptually captured.
4. Support HLL to define, access and manipulate data.
5. Provide correct access to data by multiple users.
6. Provide multiple users views.
7. Maintain data integrity.
8. Protect data.
9. Recover from failures.
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Database Management SystemDatabase Management System
Major Relational DBMS vendors/products
Paradox by Corel dBase, Clipper FoxPro, Access & SQL Server by MS MySQL DB2 by IBM Oracle, Sybase, Informix
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Advantages of Database Systems over Paper-Based Systems
1. Compactness
2. Speed
3. Less of hard work
4. Currency
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File-Based Systems (FBS)File-Based Systems (FBS)
FBS is a collection of application programs that perform tasks where each program defines and manages its own data.
DataEntry
Filehandling
File DefUser 1
Application Program 1 File1
DataEntry
Filehandling
File DefUser 2
Application Program 2 File 2
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File-Based Systems (FBS)File-Based Systems (FBS)
The limitations of the FBS approach attributed to two factors:
The definition of data is embedded in the application programs
There is no control over the access & manipulation of data beyond the imposed by the application program
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Differences between Files and a database
A database is self contained A database contains the description (system
catalog OR data dictionary OR meta data).
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File-Based Systems (FBS) File-Based Systems (FBS) DisadvantagesDisadvantages
1. Data Redundancy & Inconsistency Waste of space Cost of update Risk of inconsistency
2. Concurrent Access Anomalies3. Security Problems4. Integrity Problems5. Logical Data Dependence
Limited data sharing Inflexibility to access data Poor enforcement of standards
6. Physical Data Dependence Low programmer productivity Excessive program maintenance
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Database Systems Advantages
1. Minimal Data Redundancy
2. Logical Data Dependence Data sharing Multiple access path to data User views
3. Physical Data Dependence Application development is easy Less maintenance Good performance
4. Uniform control for security, privacy and integrity.
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Database Systems Advantages
5- Potential for enforcing standards DBA enforce standards for names and formats of data, display formats,
reports structures.
6- Reduced application development time Ex: Retrieval of data or printing a new report
7- Flexibility Change the structure without affecting the data and application programs
8- Up-to-date information is available All users access the DB. Once they save the changes the DB id available
to the other users
9- Economies of scale DBMS permits unification of data and application => reduce the cost of
operation and management
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Database Systems (DBS)Database Systems (DBS)
DBS is a single large repository of data, defined once & used by many application programs.
User 1
Application Program 1
DatabaseUser 2
Application Program 2
DataEntry
DataEntry
DBMS
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Characteristics of DB Approach
Self –Describing nature of a database system The database system contains:
Database Complete definition of the DB structure and constraints
(catalog)
Meta- Data Database
Catalog
DBMS
The DBMS works with any number of database applications
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Characteristics of DB Approach
Program-Data Independence In file based systems the structure of data files is
embedded in the access programs => any change to the structure may require changing all accessing programs
In DBMS any change in the structure does not require changing the access programs because the structure is stored in the DBMS catalog. => this is called program-data independence.
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Characteristics of DB Approach
Data Abstraction DBMS provides a conceptual representation
of the data => no much details about how the data is stored and how the operations are implemented.
There are different levels of abstraction.
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Characteristics of DB Approach
Data Abstraction
Physical Level
Conceptual Level
View 1 View 2 View 3 View N……..
How the data is stored in the
physical media (files of records
or structs)Implementers
What data is stored and how its
interrelated (tables or tree)
Database Administrators
Describe some parts of the databse
Users
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Data Models
Data Model is a set of concepts for describing the structure of a DB (data, relationships, constraints)
Used for the conceptual and view levels
Categories of data models:
- Object-based conceptual model
- Record-based logical model
- Physical model
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Categories of Data Models
Object-based conceptual model The structure of the database is flexible Data constraints specified explicitly Examples:
Entity Relationship Model (ER) Object Oriented Models (OO)
Characteristics: Entities represent things in the real world Entities are distinct New kind of entities can be constructed from old kinds
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Categories of Data Models
Record-based logical model Data viewed as a fixed- format records of
various types. Examples:
Relational model Network model Hierarchical model
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Data Models
Staff_No LName Salary Brn_No Brn_No Street Tel_No
St1 Name1 7000 1St2 Name2 4000 1St3 Name3 6500 2St4 Name4 3000 3
1 Olayaa 46300002 Malaz 47800003 Rawda 2310000
St1 Name1 7000 Olayaa 4630000
St2 Name2 4000
St3 Name3 6500
St4 Name4 3000
Malaz 4780000
Rawda 2310000
RelationalModel
NetworkModel
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Data Models
St3 Name3 6500
HierarchicalModel
St1 Name1 7000 St2 Name2 4000
St4 Name4 3000
Olayaa 4630000Malaz 4780000 Rawda 2310000
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Database Systems (DBS)Database Systems (DBS)
Staff_No FName LName DOB Salary Bno
Staff_No FName LName Age Salary Staff_No LName Bno
View 1 View 2
DBS Support of Multiple Views of Data
Virtual data derived from the data base
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Database Systems (DBS)Database Systems (DBS)
Sharing of data and multiuser transaction processing
DBMS includes concurrency control software => to ensure that several users trying to update the same data can do that in a controlled manner so the result of the update is correct.
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Actors in the SceneActors in the Scene
Database Administrator (DBA): administrates the DB, DBMS & related software
Database Designer: Identify the data & choose the appropriate structure to represent & store the data
Database user: Queries/modifies data- Naïve users: invoke one of the permanent application programs that have been written previously
- Sophisticated users: form requests in a database query language
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Actors in the SceneActors in the Scene System Analyst: determine the requirements of end users &
develop system specifications
Application Programmer: implement system specifications
DBMS designer & Implementers
Tool Developer
Operators & Maintenance Personnel
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DBS EnvironmentDBS Environment
DBMSApp
Program
DB
UserRequirement
Procedure
DBA
Naïve End User
Applicationprogrammer
DB Designer System Analyst
Sophisticated End User H/W
Design
Communicate
Manage
Write Write
Program
Use
Use
Feb 26,2008 Fatimah Alakeel 32
When Not to Use a DBMS
High initial investment in H/W, S/W and training. Generality provided by DBMS for defining and
processing data. Overhead for providing security, concurrency
control, recovery and integrity functions. Database & applications are simple, well defined,
not expected to change. Real-time requirements can not be met because of
overhead. Multiple-user access to data is not required.
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Chapter’s Summery
Definition of ( Data, Information ,Database, Database application).
Properties of (database, data stored in the database). DBMS definition, properties and responsibilities. File based system vs. database system Database system characteristics. Data models Actors in the scene. When not to use a DBMS.