Download to read offline
database slide what is database and its types .ppt
- 1. Chapter 2: DatabaseSystem Chapter 2: Database System Concepts and Architecture Concepts and Architecture Presentation slides for Presentation slides for DATABASE SYSTEMS DATABASE SYSTEMS by by Muhammad Waheed Aslam Muhammad Waheed Aslam KFUPM KFUPM Information & Computer Science Department Information & Computer Science Department
- 2. 2 Outline Outline Data Models,Schemas, and Instances Data Models, Schemas, and Instances • Categories of Data Models Categories of Data Models • Schemas, Instances, and Database State Schemas, Instances, and Database State DBMS Architecture and Data Independence DBMS Architecture and Data Independence • The Three-Schema Architecture The Three-Schema Architecture • Data Independence Data Independence Database Languages and Interfaces Database Languages and Interfaces • DBMS Languages DBMS Languages • DBMS Interfaces DBMS Interfaces
- 3. 3 Outline Outline The DatabaseSystem Environment The Database System Environment • DBMS Component Modules DBMS Component Modules • Database System Utilities Database System Utilities • Tools, Application Environments, and Communications Facilities Tools, Application Environments, and Communications Facilities Classification of Database Management Systems Classification of Database Management Systems
- 4. 4 Data Models, Schemas,and Instances Data Models, Schemas, and Instances Data Model Data Model • A collection of concepts that can be used to describe the structure of A collection of concepts that can be used to describe the structure of a database a database • By the structure we mean the data types, relationships, and By the structure we mean the data types, relationships, and constraints that should hold on the data constraints that should hold on the data • Also includes basic operations for specifying retrievals and updates Also includes basic operations for specifying retrievals and updates on the database on the database • It is becoming more common to include concepts to specify the It is becoming more common to include concepts to specify the dynamic aspect or behavior of a database application dynamic aspect or behavior of a database application
- 5. 5 Categories of DataModels Categories of Data Models Conceptual (high-level) Conceptual (high-level) • Provide concepts that are close to the way many users perceive data Provide concepts that are close to the way many users perceive data (Also called entity-based, object-based data models) (Also called entity-based, object-based data models) Physical (low-level) Physical (low-level) • Provide concepts that describe details of how data is stored in the Provide concepts that describe details of how data is stored in the computer computer • Meant for computer specialists, not for typical end users Meant for computer specialists, not for typical end users Implementation (representational) Implementation (representational) • Provide concepts that may be understood by end users but that are Provide concepts that may be understood by end users but that are not too far removed from the way data is organized within the not too far removed from the way data is organized within the computer computer • Hide some details of data storage but can be implemented on a Hide some details of data storage but can be implemented on a computer system in a direct way computer system in a direct way
- 6. 6 Schemas, Instances, andDB State Schemas, Instances, and DB State Database Schema (intension) Database Schema (intension) • The description of a database The description of a database • Not expected to change frequently Not expected to change frequently Schema Diagram Schema Diagram • A diagrammatic display of (some aspects of) a database schema. A diagrammatic display of (some aspects of) a database schema. Database State (extension) Database State (extension) • The data in the database at a particular moment of time The data in the database at a particular moment of time • Also called the current set of occurrences or instances Also called the current set of occurrences or instances • Every update operation changes the database from one state to Every update operation changes the database from one state to another another
- 7. 7 The Three-Schema Architecture TheThree-Schema Architecture Internal Schema Internal Schema • Describes the physical storage structure Describes the physical storage structure • Uses a physical data model Uses a physical data model Conceptual Schema Conceptual Schema • Describes the structure of the whole database Describes the structure of the whole database • Uses a conceptual or an implementation data model Uses a conceptual or an implementation data model External Schema External Schema • Includes a number user views Includes a number user views • Uses a conceptual or an implementation data model Uses a conceptual or an implementation data model Mappings Mappings • The process of transforming requests and results between levels The process of transforming requests and results between levels
- 8. 8 The Three-Schema Architecture TheThree-Schema Architecture
- 9. 9 Data Independence Data Independence Logical Data Independence Logical Data Independence • The capacity to change the conceptual schema without having to The capacity to change the conceptual schema without having to change the external schema or application programs change the external schema or application programs Physical Data Independence Physical Data Independence • The capacity to change the internal schema without having to The capacity to change the internal schema without having to change the conceptual schema change the conceptual schema Advantages and disadvantages Advantages and disadvantages • The three -Schema Architecture can make it easier to achieve true The three -Schema Architecture can make it easier to achieve true data independence data independence • Mappings create an overhead during compilation or execution of a Mappings create an overhead during compilation or execution of a query or a program query or a program • Not implemented fully by DBMSs Not implemented fully by DBMSs
- 10. 10 DBMS Languages DBMS Languages Data Definition Language (DDL) Data Definition Language (DDL) • Used by the DBA and database designers to define the conceptual Used by the DBA and database designers to define the conceptual schema of a a database schema of a a database • In many DBMSs, the DDL is also used to define the internal and In many DBMSs, the DDL is also used to define the internal and external schemas external schemas • In some DBMSs, separate storage definition (SDL) and view In some DBMSs, separate storage definition (SDL) and view definition language (VDL) are used to define internal and external definition language (VDL) are used to define internal and external schemas schemas Data Manipulation Language (DML) Data Manipulation Language (DML) • DML commands can be used as stand-alone (query language) or DML commands can be used as stand-alone (query language) or can be embedded within a general-purpose language can be embedded within a general-purpose language • Procedural DML - allows user to tell system exactly how to Procedural DML - allows user to tell system exactly how to manipulate data manipulate data • Non-Procedural DML - allows user to state what data is needed Non-Procedural DML - allows user to state what data is needed rather than how it is to be retrieved rather than how it is to be retrieved
- 11. 11 DBMS Interfaces DBMS Interfaces Menu-based Interfaces for Browsing Menu-based Interfaces for Browsing Forms-based Interfaces Forms-based Interfaces Graphical User Interfaces Graphical User Interfaces Natural Language Interfaces Natural Language Interfaces Interfaces for Parametric Users Interfaces for Parametric Users Interfaces for The DBA Interfaces for The DBA
- 12. 12 DBMS Component Modules DBMSComponent Modules
- 13. 13 Database System Utilities DatabaseSystem Utilities Loading Loading Backup Backup File Reorganization File Reorganization Performance monitoring Performance monitoring Other Utilities Other Utilities • Sorting files Sorting files • Handling data compression Handling data compression • Monitoring access by users Monitoring access by users
- 14. 14 Tools, Application Environments,and Tools, Application Environments, and Communications Facilities Communications Facilities CASE tools CASE tools • Used in the design phase Used in the design phase Expanded Data Dictionary(information repository) Expanded Data Dictionary(information repository) • Stores catalog information about schemas and constraints Stores catalog information about schemas and constraints • Stores other information such as design decisions, usage standards, Stores other information such as design decisions, usage standards, application program descriptions, and user information application program descriptions, and user information Application Development Environments Application Development Environments • Provide an environment for developing database applications Provide an environment for developing database applications • Include facilities for database design, GUI development, querying Include facilities for database design, GUI development, querying and updating, and application program development and updating, and application program development Communications software Communications software • Allow users to access database from remote location Allow users to access database from remote location
- 15. 15 Classification of DBMSs Classificationof DBMSs Data Model Data Model Number of Users Number of Users Number of Sites Number of Sites Cost Cost Types of Access Path Types of Access Path Purpose Purpose