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  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
  • http://ebooks.edhole.com
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Transcript

  • 1. Free Ebooks Download Mba Ebooks By Edhole Mba ebooks Free ebooks download http://ebooks.edhole.com
  • 2. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 2 Chapter 2: Database System Concepts and Architecture - Outline  Data Models and Their Categories  History of Data Models  Schemas, Instances, and States  Three-Schema Architecture  Data Independence  DBMS Languages and Interfaces  Database System Utilities and Tools  Centralized and Client-Server Architectures  Classification of DBMSs
  • 3. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 3 Data Models  Data Model:  structure of a database, the operations for manipulating these structures, and certain constraints that the database should obey.  Data Model Structure and Constraints:  Data Model Operations: Categories of Data Models  Conceptual (high-level, semantic) data models:  (Also called entity-based or object-based data models.)  Physical (low-level, internal) data models:  Implementation (representational) data models:
  • 4. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 4 Database Schema, Instance and State  Database Schema:  Includes descriptions of the database structure, data types, and the constraints on the database.  Schema Diagram:  An illustrative display of (most aspects of) a database schema.  Schema Construct:  A component of the schema or an object within the schema, e.g., STUDENT, COURSE.  Database State:  Distinction  The database schema changes very infrequently.  The database state changes every time the database is updated.  Schema is also called intension.  State is also called extension.
  • 5. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 5 Example of a Database Schema
  • 6. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 6 Example of a database state Name Student_number Class Major Smith 17 1 CS Brown 8 2 CS STUDENT
  • 7. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 7 Three-Schema Architecture  Defines DBMS schemas at three levels:  Internal schema  Conceptual schema  External schemas at the external level to describe the various user views.  Usually uses the same data model as the conceptual schema. Data Independence:  Logical Data Independence:  Physical Data Independence:
  • 8. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 8 DBMS Languages  Data Definition Language (DDL)  Data Manipulation Language (DML)  High-Level or Non-procedural Languages: These include the relational language SQL  May be used in a standalone way or may be embedded in a programming language. Also called declarative langauages  Low Level or Procedural Languages:  These must be embedded in a programming language http://ebooks.edhole.com
  • 9. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 9 DBMS Interfaces  Stand-alone query language interfaces  Example: Entering SQL queries at the DBMS interactive SQL interface (e.g. SQL*Plus in ORACLE)  Programmer interfaces for embedding DML in programming languages  User-friendly interfaces  Menu-based, forms-based, graphics-based, etc.
  • 10. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 10 DBMS Programming Language Interfaces  Embedded Approach: e.g embedded SQL (for C, C++, etc.), SQLJ (for Java)  Procedure Call Approach: e.g. JDBC for Java, ODBC for other programming languages  Database Programming Language Approach: e.g. ORACLE has PL/SQL  Menu-based, popular for browsing on the web  Forms-based, designed for naïve users  Graphics-based  Natural language: requests in written English  Combinations of the above:  Speech as Input and Output  Web Browser as an interface  Parametric interfaces, e.g., bank tellers using function keys.  Interfaces for the DBA:
  • 11. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 11 Database System Utilities  To perform certain functions such as:  Loading data stored in files into a database. Includes data conversion tools.  Backing up the database periodically on tape.  Reorganizing database file structures.  Report generation utilities.  Performance monitoring utilities.  Data dictionary / repository:  Application Development Environments and CASE (computer-aided software engineering) tools:  Examples:  PowerBuilder (Sybase)  JBuilder (Borland)  JDeveloper 10G (Oracle) http://ebooks.edhole.com
  • 12. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 12 Typical DBMS Component Modules
  • 13. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 13 A Physical Centralized Architecture
  • 14. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 14 Logical two-tier client server architecture
  • 15. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 15 Three-tier client-server architecture
  • 16. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 16 Classification of DBMSs  Based on the data model used  Traditional: Relational, Network, Hierarchical.  Emerging: Object-oriented, Object-relational.  Other classifications  Single-user vs. multi-user.  Centralized vs. Distributed  Homogeneous DDBMS vs Heterogeneous DDBMS  Federated or Multidatabase Systems  Distributed Database Systems  Based on cost factors
  • 17. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1- 17 History of Data Models  Network Model  Hierarchical Model  Relational Model  Object-oriented Data Models  Object-Relational Models