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.
- 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
|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
|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
- 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:
|Quick Review on relationships :
- Teacher teaches :
- Class : contains :
- Class requires: Classroom.
Riddle of Relation
- Teacher may teach many classes, but each class is taught by one
- One to Many : Teacher
- A Class contains many students, each student may take many
- 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