INTRODUTION OF ORACLE

1) what is file?

 A stream of bytes or characters.
It built with an operating system.

2) Disadvantages of File?

 A stream of bytes or characters.
No support of data type.
It will not support to store or allocate memory dynamically.
Data Control is share with multiple users-that causes concurrent users problem(More than one user access the same resource at a time called as concurrent users).
File does not support compatibility.

                                         

3) What is Data ?

 Data is set of items.
Data as an abstract concept can be viewed as the lowest level of abstraction from which information and then knowledge are derived.
For data to become information, it must be interpreted and take on a meaning.
A report containing practical information on the best way to understand the object is called as knowledge.

4) What is Database ?

 A Database is an organized collection of information, so that it can easily be accessed, managed, and updated.
The most prevalent approach is the Relational Database, a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways.
A Distributed Database is one that can be dispersed or replicated among different points in a network.
An Object-oriented programming database is one that is congruent with the data defined in object classes and subclasses.
in database management system (DBMS), data files are the files that store the database information, whereas other files, such as index files and data dictionaries, store administrative information, known as metadata.

5) What is DBMS ?

 To manage DB you need DBMS.
A DBMS is a program that stores, retrieves and modifies data in a DB on request.
There are 4 main types of DBs:
Hierarchical
Network
Relational
Object Relational
A hierarchical database model is a data model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children, but each child has only one parent (also known as a 1-to-many relationship).

                                           

 A hierarchical database model is a data model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children, but each child has only one parent (also known as a 1-to-many relationship).
A network database model allows each record to have multiple parent and child records, forming a generalized graph structure. It uses physical links to establish relations.

                                         

 In a network model, data are accessed one record at a time. This males it essential for the database designers, administrators, and programmers to be familiar with the internal data structures to gain access to the data. Therefore, a user friendly database management system cannot be created using the network model.
Its dependent on 'C language' in order to create relationships.
A RDBMS database model allows to store data logically in the form of table( rows and columns).
Data is physically stored in data files not in table.
Interaction of rows and columns(i.e.- cell) gives us a value.
No data duplication/redundancy, No need of physically links.
Relation is maintained through primary keys and foreign keys.
Data can be stored/accessed by several users.
Supports unlimited size and supports data types.
Provided high security.
It supports E.F. Code rules.
According to the E.F. Code rules, the DB which supports < 6 E.F. Code rules is called as DBMS technology.
the DB which supports = 6 E.F. Code rules is called as semi- RDBMS technology.
the DB which supports > 6 E.F. Code rules is called as RDBMS technology.

                                          

 An object-relational database (ORD), or object-relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language. In addition, just as with proper relational systems, it supports extension of the data model with custom data-types and methods.
The main benefit to this type of database lies in the fact that the software to convert the object data between a RDBMS format and object database format is provided. Therefore it is not necessary for programmers to write code to convert between the two formats and database access is easy from an object oriented computer language.

                                     

6) RDBMS vs. ORDBMS:

 A Relational Database Management System (RDBMS) is a Database Management System (DBMS) that is based on the relational model. Most popular DBMSs currently in use are RDMSs. Object-Relational database (ORDBMS) is also a DBMS that extends RDBMS to support a broader class of applications and attempts to create a bridge between relational and object-oriented paradigms.
ORDBMS puts an object oriented front end on a RDBMS. When an application communicates with an ORDBMS it will normally act as though the data is stored as objects. Then the ORDBMS will convert the object information into data tables with rows and columns and handle the data as it were stored in a RDBMS. Further, when the data is retrieved, it will return a complex object created by reassembling the simple data. Biggest advantage of ORDBMS is that it provides methods to convert data between RDBMS format and OODBMS format, so that the programmer does not need to write code to convert between the two formats and the database access is easy from an object oriented language.
Even though RDBMS and ORDBMS are both DBMSs, they differ in how they interact with applications. Applications using RDBMS has to do extra work when storing complex data while ORDBMS inherently provide support for this. But due to the internal conversion between data formats, performance of ORDBMSs can be degraded. Therefore choosing one over the other is dependent on the data that needs to be stored/ managed.
Entity Relationship Model
In an effective system, data is divided into discrete categories or entities. And ER model is an illustration of various entities in a business and the relationship between them. ER model separate the information required by business from the activities performed by business. Although business can change the activities , the type of information remains constant.
Benefits:
Documents information for the organization in a clear format.
Provides an easily understood pictorial map for the DB design.
Offers an effective framework for integrating multiple applications.
Entity: a thing of significance about which informaiton need to be know.
Ex- Employees, Departments ...
Atribute: something that discribes an entity.
Ex- form employee Entity: ID, Name, Job, hire date, department...
Relationship: A named association between entities showing optionality and degree.
Ex: Employees and Departments

 

Entity
Soft Box
singular, unique name
Uppercase
Synonym in parentheses
Attributes
singular name
Lowercase
Mandatory marked with "*"
Optional marked with "o"
Unique Identifier
Primary Marked with "#"
Secondary marked with "(#)"
Dashed line Optional elements indicating "may be"
Sloid line Mandatory elements indicating "must be"
Crow's foot Degree elements indicating "one or more"
Single line Degree elements indicating "oneand only one"
 
 
#* Employee ID
Employee
* name
o Job title
  \
   \
    ----------
   /
  /
Department
#* Department ID
* name
o Location

 

7) What is Cardinality ?

 A relationship’s cardinality defines the maximum number of entities of one type that can be associated with an entity of another type.
1:1 --- one-to- one --- One entity of type X can be associated with, at most, one entity of type Y. One entity of type Y can be associated with, at most, one entity of type X.
An example: the relationship between car and steering wheel. A car has only one steering wheel and a steering wheel can only be installed in one car.
1:M --- one-to-many --- One entity of type X can be associated with many entities of type Y. One entity of type Y can be associated with, at most, one entity of type X.
An example: the relationship between building and rooms. A building can have many rooms but a room can be in, at most, one building.
M:M --- many-to-many --- One entity of type X can be associated with many entities of type Y. One entity of type Y can be associated with many entities of type X.
An example: the relationship between a car and its options (such as air conditioning, ABS brakes). A car can have many options and an option can be installed on many cars. 

Oracle has two Products:
Oracle9i Application server and Oracle9i DB, this provided a complete and simple infrastructure for Internet Applications.
Oracle9i AS stores all your applications and Oracle9iDB stores all your data.
Oracle9iAS is the only AS to include services for all the different server applications you want to run.
Ex: web sites, Java applications, BI applications
It also provided integration between users, applications and data through out your organization.
Oracle9iDB manages all your data. This is not only object relational data, it can also be unstructured data:
Spreadsheets, word documents, PowerPoint presentations, XML, MP3, Graphics, video…
The data does not even have to be in the DB. Oracle9i DB has services through which you can store metadata about information stored in the file system, you can user the DB server to manage and server information wherever it is located.