Elmasri_6e_GE Ch 1.ppt

Chapter 1 Introduction to Databases Copyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-Wesley  Chapter 1 Outline  Introduction  An Example  Characteristics of the Database Approach  Actors on the Scene  Workers behind the Scene ...

Chapter 1 Introduction to Databases Copyright © 2011 Pearson Education, Inc. Publishing as Pearson Addison-Wesley  Chapter 1 Outline  Introduction  An Example  Characteristics of the Database Approach  Actors on the Scene  Workers behind the Scene  Advantages of Using the DBMS Approach  A Brief History of Database Applications  When Not to Use a DBMS Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Overview  Traditional database applications  Store textual or numeric information  Multimedia databases  Store images, audio clips, and video streams digitally  Geographic information systems (GIS)  Store and analyze maps, weather data, and satellite images Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Overview (cont'd.)  Data warehouses and online analytical processing (OLAP) systems  Extract and analyze useful business information from very large databases  Support decision making  Real-time and active database technology  Control industrial and manufacturing processes Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Introduction  Database  Collection of related data  Known facts that can be recorded and that have implicit meaning  Miniworld or universe of discourse (UoD)  Represents some aspect of the real world  Logically coherent collection of data with inherent meaning  Built for a specific purpose Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Introduction (cont'd.)  Example of a large commercial database  Amazon.com  Database management system (DBMS)  Collection of programs  Enables users to create and maintain a database  Defining a database  Specify the data types, structures, and constraints of the data to be stored Copyright © 2011 Ramez Elmasri and Shamkant Navathe Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Introduction (cont'd.)  Meta-data  Database definition or descriptive information  Stored by the DBMS in the form of a database catalog or dictionary  Manipulating a database  Query and update the database miniworld  Generate reports Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Introduction (cont'd.)  Sharing a database  Allow multiple users and programs to access the database simultaneously  Application program  Accesses database by sending queries to DBMS  Query  Causes some data to be retrieved Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Introduction (cont'd.)  Transaction  May cause some data to be read and some data to be written into the database  Protection includes:  System protection  Security protection  Maintain the database system  Allow the system to evolve as requirements change over time Copyright © 2011 Ramez Elmasri and Shamkant Navathe  An Example  UNIVERSITY database  Information concerning students, courses, and grades in a university environment  Data records  STUDENT  COURSE  SECTION  GRADE_REPORT  PREREQUISITE Copyright © 2011 Ramez Elmasri and Shamkant Navathe  An Example (cont'd.)  Specify structure of records of each file by specifying data type for each data element  String of alphabetic characters  Integer  Etc. Copyright © 2011 Ramez Elmasri and Shamkant Navathe  An Example (cont'd.)  Construct UNIVERSITY database  Store data to represent each student, course, section, grade report, and prerequisite as a record in appropriate file  Relationships among the records  Manipulation involves querying and updating Copyright © 2011 Ramez Elmasri and Shamkant Navathe  An Example (cont'd.)  Examples of queries:  Retrieve the transcript  List the names of students who took the section of the ‘Database’ course offered in fall 2008 and their grades in that section  List the prerequisites of the ‘Database’ course Copyright © 2011 Ramez Elmasri and Shamkant Navathe  An Example (cont'd.)  Examples of updates:  Change the class of ‘Smith’ to sophomore  Create a new section for the ‘Database’ course for this semester  Enter a grade of ‘A’ for ‘Smith’ in the ‘Database’ section of last semester Copyright © 2011 Ramez Elmasri and Shamkant Navathe  An Example (cont'd.)  Phases for designing a database:  Requirements specification and analysis  Conceptual design  Logical design  Physical design Copyright © 2011 Ramez Elmasri and Shamkant Navathe Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Characteristics of the Database Approach  Traditional file processing  Each user defines and implements the files needed for a specific software application  Database approach  Single repository maintains data that is defined once and then accessed by various users Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Characteristics of the Database Approach (cont'd.)  Main characteristics of database approach  Self-describing nature of a database system  Insulation between programs and data, and data abstraction  Support of multiple views of the data  Sharing of data and multiuser transaction processing Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Data Abstraction  Data abstraction  Allows program-data independence and program-operation independence  Conceptual representation of data  Does not include details of how data is stored or how operations are implemented  Data model  Type of data abstraction used to provide conceptual representation Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Self-Describing Nature of a Database System  Database system contains complete definition of structure and constraints  Meta-data  Describes structure of the database  Database catalog used by:  DBMS software  Database users who need information about database structure Copyright © 2011 Ramez Elmasri and Shamkant Navathe Copyright © 2011 Ramez Elmasri and Shamkant Navathe Support of Multiple Views of the Data  View  Subset of the database  Contains virtual data derived from the database files but is not explicitly stored  Multiuser DBMS  Users have a variety of distinct applications  Must provide facilities for defining multiple views Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Sharing of Data and Multiuser Transaction Processing  Allow multiple users to access the database at the same time  Concurrency control software  Ensure that several users trying to update the same data do so in a controlled manner Result of the updates is correct  Online transaction processing (OLTP) application Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Actors on the Scene  Database administrators (DBA) are responsible for:  Authorizing access to the database  Coordinating and monitoring its use  Acquiring software and hardware resources  Database designers are responsible for:  Identifying the data to be stored  Choosing appropriate structures to represent and store this data Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Actors on the Scene (cont'd.)  End users  People whose jobs require access to the database  Types Casual end users Naive or parametric end users Sophisticated end users Standalone users Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Actors on the Scene (cont'd.)  System analysts  Determine requirements of end users  Application programmers  Implement these specifications as programs Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Advantages of Using the DBMS Approach  Controlling redundancy  Data normalization  Denormalization Sometimes necessary to use controlled redundancy to improve the performance of queries  Restricting unauthorized access  Security and authorization subsystem  Privileged software Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Advantages of Using the DBMS Approach (cont'd.)  Providing backup and recovery  Backup and recovery subsystem of the DBMS is responsible for recovery  Providing multiple user interfaces  Graphical user interfaces (GUIs)  Representing complex relationships among data  May include numerous varieties of data that are interrelated in many ways Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Advantages of Using the DBMS Approach (cont'd.)  Enforcing integrity constraints  Referential integrity constraint Every section record must be related to a course record  Key or uniqueness constraint Every course record must have a unique value for Course_number  Business rules  Inherent rules of the data model Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Advantages of Using the DBMS Approach (cont'd.)  Additional implications of using the database approach  Reduced application development time  Flexibility  Availability of up-to-date information  Economies of scale Copyright © 2011 Ramez Elmasri and Shamkant Navathe  When Not to Use a DBMS  More desirable to use regular files for:  Simple, well-defined database applications not expected to change at all  Stringent, real-time requirements that may not be met because of DBMS overhead  Embedded systems with limited storage capacity  No multiple-user access to data Copyright © 2011 Ramez Elmasri and Shamkant Navathe  Summary  Database  Collection of related data (recorded facts)  DBMS  Generalized software package for implementing and maintaining a computerized database  Several categories of database users  Database applications have evolved  Current trends: IR, Web Copyright © 2011 Ramez Elmasri and Shamkant Navathe