SD01 overview dbms

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ITM 625 – [01] DBMS OverviewITM 625 – [01] DBMS Overview 22

ObjectivesObjectives

To understand the following concepts: To understand the following concepts:

1.1.DatabaseDatabase

2.2. Three levels of database views Three levels of database views

3.3.ER diagramER diagram4.4.SQLSQL

5.5.DBMSDBMS




DatabaseDatabase

AA databasedatabase is a collection of interrelatedis a collection of interrelateddata stored within a computerdata stored within a computerenvironment.environment.

Two characteristics are: Two characteristics are:Large data volumeLarge data volume

PersistentPersistent

Examples: info of students, travelExamples: info of students, travelreservations and banking.reservations and banking.




DatabaseDatabase

A databaseA database can be viewed in 3 levels:can be viewed in 3 levels:

1.1.Conceptual modelingConceptual modeling

2.2.Logical modelingLogical modeling

3.3.Physical modelingPhysical modeling




Conceptual LevelConceptual Level

It permits us to model the application of It permits us to model the application of the world which is independent of anythe world which is independent of anyparticular data (logical) modelparticular data (logical) model

It provides a framework for developing aIt provides a framework for developing adatabase schema from the top to thedatabase schema from the top to thebottom in the process of a databasebottom in the process of a databasedesigndesign

Presentations:Presentations:1.1.Entity-relationship (ER) modelEntity-relationship (ER) model

2.2.Object-oriented modelObject-oriented model

3.3.Unified modeling technique (UMT)Unified modeling technique (UMT)




Entity-relationshipEntity-relationship

The main components are: The main components are:

– Entity Entity : a thing that exists and is: a thing that exists and isdistinguishable.distinguishable.

– Attribute Attribute: describes properties of : describes properties of entities and relationships.entities and relationships.

– RelationshipRelationship: a connection between: a connection betweenentities.entities.

– Key Key : differentiates one entity instance: differentiates one entity instancefrom all others in the entity.from all others in the entity.




Entity-relationshipEntity-relationship

Mapping cardinality: indicates the number of Mapping cardinality: indicates the number of instances in entity E1 that can or must beinstances in entity E1 that can or must beassociated with instances in entity E2:associated with instances in entity E2:

1.1.One to one relationshipOne to one relationship

2.2.Many to one relationshipMany to one relationship

3.3.Many to many relationshipMany to many relationship




ER DiagramER Diagram




UML DiagramUML Diagram




Logical LevelLogical Level

Database schemaDatabase schema is defined to describeis defined to describethe structure & constraint of informationthe structure & constraint of informationmanaged by the application in a Datamanaged by the application in a DataDefinition Language (Definition Language (DDLDDL).).

Query languageQuery language is used to insert,is used to insert,update, delete and query the data in aupdate, delete and query the data in aData Manipulation Language (Data Manipulation Language (DMLDML).).

This level is described as a set of This level is described as a set of

relatively simple structures.relatively simple structures.




SQLSQL

SQL (Standard Query Language)SQL (Standard Query Language) is theis thewidely accepted language used in allwidely accepted language used in allrelational database.relational database.

Characteristics:Characteristics:

1.1.Declarative: express whatDeclarative: express whatexpected, without knowing how it isexpected, without knowing how it isprocessedprocessed

2.2.Based on mathematics: relationalBased on mathematics: relational

calculus and algebracalculus and algebraBut it lacks of iteration.But it lacks of iteration.




Logical LevelLogical Level




Physical LevelPhysical Level

StorageStorage: efficient organization of data: efficient organization of data Access Methods Access Methods: accelerate data: accelerate data

retrieval by defining data structures orretrieval by defining data structures or

index.index.

Query ProcessingQuery Processing: to answer a query: to answer a query Query OptimizationQuery Optimization: to evaluate of query: to evaluate of query

processingprocessing

Concurrency and recovery Concurrency and recovery : to manage: to manageconcurrent access to data and resourcesconcurrent access to data and resources




Physical LevelPhysical Level

Examples:




DBMSDBMS

AA DBMS (Database Management System)DBMS (Database Management System) is ais acollection of software that manages thecollection of software that manages thedatabase structure and controls access.database structure and controls access.

It performs the data:It performs the data:

Definition: types, structures & constraintsDefinition: types, structures & constraints

Construction: storageConstruction: storage

ManipulationManipulation

QueryQuery

UpdateUpdate




Evolution of DatasetsEvolution of Datasets




Towards Free DBMS Towards Free DBMS

There is a trend that big commercial There is a trend that big commercialdatabase vendors release the free licensedatabase vendors release the free licenseof DBMS (with some limitations) such as:of DBMS (with some limitations) such as:

Microsoft SQL Server 2005 Express EditionMicrosoft SQL Server 2005 Express Edition

Oracle 10gOracle 10g




Free DBMSFree DBMS

SD01 overview dbms

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