Database_Intro1.htm
Introducing Database:

database—is the collection of interrelated stored data that available to the multiple users within one or more organizations; a collection of tables constitute a db in  the relational model.

 

The sole purpose of the database is to store and retrieve relevant data at ease.

In the above scenario, the metadata (data about the data) provides a description of  the data characteristics and the relationships that link the data found within the database.
Basic Info:
  • data : raw facts
  • field : group of characters with a common data type
  • record : logically connected a set of one more fields
  • file : collection of related records.
File System VS Database

A File System

A Database:

Drawback of file system
  • Redundancy : duplicate fields across the organization., which may also cause data inconsistency. Any change in the data should be corrected, in all the relevant files. 
  • Inconstancy : Data Entry error like different phone number entered in another file location, e.g. 630-539-2125 rather than 630-529-2125
 
Objectives of Database Management
  • Data Dictionary: a rationale of data relationship ( metadata)
  • Efficient Data Storage Management
  • Data transformation and presentation: DBMS translates "logical " requests into a command that 'physically " locate / retreive that data.
  • Enforces security
  • Multiuser access controls
  • Backup and recovery
  • Provides access to the data via a query language
  • A relational model [codd, 1970] is rested on "tuples" of name and value pairs.
  • Relations are collections of tuples have a mathematical foundation based on set theory.
 
 
About Oracle Database
 
  • Oracle Database is a relational database with object and Extensible Markup Language (XML) capabilities.
  • All data is stored in two-dimensional tables that are composed of rows and columns.

In a relational database, Oracle Database enables you to store data, update it, and efficiently retrieve it, with a high degree of performance, reliability, and scalability.
 
Data Base Models:

Hierarchical

 
Quick Review on relationships :

  • Teacher teaches :
    • Class : contains :
      • Students
    • Class requires: Classroom.

    Riddle of Relation

  • Teacher may teach many classes, but each class is taught by one teacher
    • One to Many : Teacher to Class
  • A Class contains many students, each student may take many classes
    • Many To Many : relations between Student : Class
  • A class requires a classroom at one time slot in a day, ( many  times in a day)
    • One To Many relation between Class and Classroom