Dsecribing Database..

A database plays a very important role in creating a dynamic and easy -to-personalize Web site. With the use of databases, Web sites become more powerful than those created in static HTML.

A database comprises information in structured and organized form that can easily be accessed and manipulated. According to the needs of a Web site, the database can be very large or minimal in size. A database can be stored on a single PC or on a collection of high-powered database servers depending upon the size. When a database is stored in a collection of servers, it is known as a distributed database.

What is a Database?

A database is a collection of relevant data that is interconnected and organized systematically so that its contents can easily be accessed, managed, and updated electronically.

Database Users:

Users can be divided into the following three categories:

Database Administrator: He is the person who possesses complete information of the database and has centralized control over it. He also has full control over schema definitions, integrity checks, privileges/rights of users. Only a database administrator can provide the rights to other users for accessing the database.

Application Programmers: They are programmers who write application programs for data access in a specific environment and solve specific database problems.

Sophisticated Programmers: They are the ones who have the right to interact with the database without writing any program. They can update the data by using commands of a database query language such as SQL.

Basics of Database Structure

The structure of a database is technically defined by a schema. A schema is a collection of database objects, such as tables, views, sequences, synonyms, clusters, indexes, database links, procedures, functions, and packages. A schema is owned by a database user and has the same name as that of the user. It defines what kind of information is stored in the database and how it is stored.

Database Objects
Database objects are used to store data, access stored data, restrict data access, and speed up data access. Following are the primary database objects:

Table: A table is the basic unit of data storage in a database. It is composed of columns and rows. A column is the vertical space in a database table, which represents a particular domain of data. The intersection of a single row and column is known as a field. Each field in the database has a type associated with it. Some common types are text, numeric, and blob. The text type is used for storing lingo strings, numeric type is for storing floats and integers, and blob type is for storing media and picture. A row is a collection of data in columns corresponding to a single record.

Types of Databases

Databases may be of three types – Relational database, Distributed database, and Object-oriented database.

Relational database: Relational database is a collection of related data. This database is in the form of tables. Rows and columns of the table represent relationship between the data. In a Relational database, the data can be obtained from two or more tables to create a third table. If data is changed in one table, it will reflect in all the related tables. For searching the data within the database, a query language is used.

Distributed database: It is a database that is stored on more than one computer and each computer can share its data with the others through some form of communications network. A distributed database requires database server software on each of the different computers where the data is stored that allows users or programs to work on the database as if they had access to the whole database locally.

Object-oriented database: It is one that is congruent with the data defined in object classes and subclasses.

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