Tuesday, May 22, 2012

Introduction to DBMS

A DBMS is a software package for managing a database. A database is a collection of related data.
Example DBMSs: Oracle, DB2, Informix, Ingres, ….

Position Of a DBMS

A DBMS interacts with the Operating System and System resources: memory, processor, IO, File System, Security subsystem.

A DBMS interacts with Users. Users may be Database Administrators (DBA): designers, implementers, maintainers, Database End-users: Casual or professional

Three level Architecture (ANSI/SPARC)

Differences between Three Levels

Internal Schema

Struct Staff {   
                      int Staff_No, Branch_No;
                      char Fname[15];
                      char Lname[15];
                      struct date Date_of_Birth;
                      float Salary;
                      index Staff_No;

Data Independence

Logical Data Independence: Capacity to change the conceptual schema without having to change external schema's or application programs
Physical Data Independence: Capacity to change the internal schema without having to change conceptual or external schema's

Database Views

Kinds of Databases

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