Sunday, 26 August 2018

know about Oracle Database

Oracle Database

Oracle database manage all your data. This is not just the object-relational data that you expect an enterprise database to manage. Oracle database is one of the most trusted and safe database engines. Oracle database developed in 1970 by Lawrence Ellison. Oracle database is not just object-relational data, it can also manage unstructured data like:
  • Text Files: Word documents, Spreadsheets.
  • XML.
  • PowerPoint Presentations. 
  • Multimedia: Audio, Video etc. 
  • Web Documents.
The data does not even have to be in the database. Oracle database has services through which you can store metadata about information stored in file systems. You can use the database server to manage your data where it is located from anywhere.
Oracle database specially designed for online development and deployment platform. Oracle has the high and safe technology of data management. Oracle database’s online features help any organization and programmers build online-savvy applications access across platforms and across the enterprise. In Oracle database, online data transaction very safe with fast processing compares than other databases.

Relational Database Management System

Oracle database is a relational database system. Oracle database also is known as RDBMS. The Oracle server always enhances the data modeling capabilities to support the object-relational database model that brings object-oriented programming, complex data types, complex business objects and fully compatible with it.

In Oracle database many features for improved performance and functionality of online transaction processing (OLTP). It is capable of supporting transaction-oriented on the internet. Basically, OLTP systems use for any data entry, business transaction, retail sales data etc. It benefits from enhancements such as parallel execution of insert, update, delete operations and query optimization. Oracle online supports client-server and web-based applications that are distributed and multitiered.

Oracle is a fully scalable relational database architecture, which is often used by multi-national-companies, which also manage and process their data across the globe and on the local area network. To allow communication over the network, the Oracle database has its network components. Oracle online database can enhance thousands of concurrent users, and tackle any type of data which can text data, spatial data, image data, multimedia data like image, audio, video etc. and time stamp data as traditional structured data.

Definition of RDBMS:- Relational database based on a collection of relations or between two-dimensional tables specified by Dr. E.F. Codd in 1970 called “A Relational model of data for large shared data banks.” Dr. Codd purposed the relational model for the database system.

Suppose, you want to store information about all the employees in your company. In a relational database, you have to create several tables to store different pieces of information about your employees, such as an Emp table (Employees), Dept Table (Department), Sal Table (Salary).

Data Models

Before creating tables, you have to create data models. System designers develop models to explore ideas and improve the understanding of the database design. Models help communicate concepts in people’s minds. They can be used to do the following:
  • Communicate.
  • Categorize.
  • Describe.
  • Specify.
  • Investigate.
  • Evolve.
  • Analyse.
  • Imitate.

The objective is to produce a model that fits a multitude of these uses, can be understood by an end user, and contains sufficient details for a developer to build a database system.

Entity Relationship

In an effective system, data is divided into discrete categories and entities. An entity-relationship model is an illustration of various entities in a business and the relationship between them. The ER model separate the information required by a business from the activities performed with a business. Although business can change their activities, the type of information tends to remain constant. Therefore, the data structure also tends to be constant.

Benefits of ER Modelling is information of any organization’s documents in a clear view and in good prescribed format. With this clear picture comes on the front of the scope of the information required. We can easily understand this design with help of this can create database design easily. We can create a good and suitable framework for integrating multiple applications.

The relationship between Multiple Tables

We know that in every database all entries always save in a table. In database have multiple tables. A relationship is a connection between two tables those contains data. In our database have one table named EMP and second table named Dept. In the Emp table contains information about employees and the Dept table contains information about the department.

Now we know well data about different entities are stored in different tables. If you want to combine two or more tables to fetch particular reason. For example, you want to know the location of the department where your employee works, basically, you want the employee’s location. In this situation, you have to know employee’s information from Emp Table and have to know department’s information from Dept table. With the help of RDBMS, you have to relate the data in one table to the data in another by using the foreign key. A foreign key is a column that refers to a primary key in the same table or another table. In simple words, you have to join Emp Table with Dept Table relation by Emp ID. (Emp.ID=Dept.ID).

Some Guidelines for Keys
  • In which column you created a primary key, you can’t enter a duplicate value.
  • In one table we can create only one primary key, Primary key have a unique identity.
  • Basically, a primary key generally can’t be changed. 
  • A foreign key is based on data values and is purely logically, not physical, pointers.
  • A foreign key value must match an existing primary key or unique key value, or else be null.
  • A foreign key must reference either a primary key or unique key column. 
  • Primary key basically always in the parent table and Foreign Key in other like child table.
In the relational database, we do not specify the access route to the table, and we do not need to know the data is arranged physically. In database stored data in a structured format always using rows and columns. If you want to fetch data from the database, you have to execute Structure Query Language (SQL). This is the American national standards Institute (ANSI). This SQL used for operating the relational database.

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