database concept

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Chapter 1

Introduction To Database and DB UsersIntroduction To Database and DB Users

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IntroductionIntroduction

• Databases have become an integral part of many computer systems.

• Ranging from complex systems that control air traffic, plant operation, and stock market transactions to general purpose computing systems that run textual, audio and video applications.

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Basic DefinitionsBasic Definitions• Data: Known facts that are recorded &

have implicit meaning.• Information: Data processed to be useful

in decision making• Metadata: Data that describes data. • Database (DB): A collection of related

data.• Database Management System

(DBMS): A software package to facilitate the creation and maintenance of a computerized database.

• Database System (DBS): The DBMS software together with the data itself.

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Types of DatabasesTypes of Databases

• TraditionalTraditional DBs e.g. numeric and textual.• MultimediaMultimedia DBs e.g. sounds and video clips.• Geographic Information SystemsGeographic Information Systems (GIS) i.e. maps

and weather data.• DataData WarehousesWarehouses e.g. archives (DSS).• MobileMobile DBs. Recent advances in wireless

technologies have led to mobile computing. DBs:– Vertical. Limited access i. e. Parking availability

at an airport.– Horizontal. public (Stock prices).

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The Range of Database ApplicationsThe Range of Database Applications

Personal Database.– Standalone desktop database.

Workgroup Database.– Local area network (<25 users).

Department Database.– Local area network (25-100 users).

Enterprise Database.– Wide-area network (100’s or 1000’s of

users).

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Personal DatabasePersonal Database

• Desktop database systems typically:– Have one application.– Have only a few tables.– Less than ten thousand records.– Are simple in design.– Involve only one computer.– Support one user at a time.

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Workgroup database with local area network

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Database SystemDatabase System

• Supports operations:– Add or delete files to the database.– Insert, retrieve, remove, or change

data in database.

• Components:– Data, hardware, software, users.

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Database System - DataDatabase System - Data

• May support single or many users.• Many users in organizations:

–Data is integrated.–Data is shared.

• Different users will require different views.

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Database System - HardwareDatabase System - Hardware

• Data is stored on Disk.•Direct access to subset portions.•Rapid I/O.

• Data operated on in main memory.

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Database System - SoftwareDatabase System - Software

• Database management system (DBMS).

• DBMS provided by specific vendor.– Microsoft Access.– Microsoft’s SQL Server.– Oracle’s Oracle.– IBM’s DB2.– NCR Teradata.

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Database Applications

• A database application is a set of one or more computer programs that serves as an intermediary between the user and a DBMS.

• A database application reads, writes, formats, and/or modifies data. Applications produce:– Forms.– Queries.– Reports.– Else.

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Functions of a Database Application

• Create and process forms• Create and process queries• Create and process reports• Execute application logic• Provide control

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Typical DBMS Functionality

Other features:– Protection or Security measures to

prevent unauthorized access.– Presentation and Visualization of data.

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Example of a DatabaseExample of a Database(with a Conceptual Data Model)(with a Conceptual Data Model)

• Mini-world for the example: Part of a UNIVERSITY environment.

• Some mini-world entities:– STUDENTs.– COURSEs.– SECTIONs.– DEPARTMENTs.– INSTRUCTORs.

Note: The above could be expressed in the ENTITY-RELATIONSHIP data model.

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Example of a DatabaseExample of a Database(with a Conceptual Data Model)(with a Conceptual Data Model)

• 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.

Note: The above could be expressed in the ENTITY-RELATIONSHIP data model.

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Main Characteristics of the Database Main Characteristics of the Database ApproachApproach

• Insulation between programs and data: Called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs.

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Main Characteristics of the Database Main Characteristics of the Database ApproachApproach

• 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.

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Main Characteristics of the Database Main Characteristics of the Database ApproachApproach

• Sharing of data and multi-user transaction processing : allowing a set of concurrent users to retrieve and to update the database. Concurrency control within the DBMS guarantees that each transaction is correctly executed or completely aborted.

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Database UsersDatabase Users

• Users may be divided into:

– Those who actually use and control the content (called “Actors on the Scene”); and

– Those who enable the database to be developed and the DBMS software to be designed and implemented (called “Workers Behind the Scene”).

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Database UsersActors on the scene

– Database administrators: responsible for authorizing access to the database, for coordinating and monitoring its use, acquiring software, and hardware resources, controlling its use and monitoring efficiency of operations.

– Database Designers: responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs.

– End-users: they use the data for queries, reports and some of them actually update the database content.

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Historical Development of Database Technology

• Early Database Applications: The Hierarchical and Network Models were introduced in mid 1960’s and dominated during the seventies. A bulk of the worldwide database processing still occurs using these models.

• Relational Model based Systems: The model that was originally introduced in 1970 was heavily researched and experimented with in IBM and the universities. Relational DBMS Products emerged in the 1980’s.

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Historical Development of Database Technology

• Object-oriented applications: OODBMSs were introduced in late 1980’s and early 1990’s to cater to the need of complex data processing in CAD and other applications. Their use has not taken off much.

• Data on the Web and E-commerce Applications: Web contains data in HTML (Hypertext markup language) with links among pages. This has given rise to a new set of applications and E-commerce is using new standards like XML (eXtended Markup Language).

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Key Fields

• Keys are special fields that serve two main purposes:– Primary keys are unique identifiers of the relation in question.

Examples include employee numbers, social security numbers, etc. This is how we can guarantee that all rows are unique

– Foreign keys are identifiers that enable a dependent relation (on the many side of a relationship) to refer to its parent relation (on the one side of the relationship)

• Keys can be simple (a single field) or composite (more than one field)

• Keys usually are used as indexes to speed up the response to user queries (More on this in Ch. 6)

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Figure 5-3 -- Schema for four relations (Pine Valley Furniture)

Primary Key

Foreign Key (implements 1:N relationship between customer and order)

Combined, these are a composite primary key (uniquely identifies the order line)…individually they are foreign keys (implement M:N relationship between order and product)