Sunday, February 6, 2011

Databases

Databases
A database is an integrated collection of logically related records or files. Databases can be classified according to types of content: bibliographic, full-text, numeric, and image. The data in a database is organized according to a database model. There are three different types of database models: Relational model, Hierarchical model and the Network model.
Database models:
1. Relational model: relational model represents data and relationship among data by collection of tables.
2. Hierarchical model: Hierarchical model represents data and relationship among data by records and links respectively.
3. Network model: Network model represents data and relationship among data in terms of graphs.

Types of Databases:

1.Operational database

Operational databases store detailed data needed to support the operations of the entire organization. They are also called subject-area databases (SADB) or transaction databases or production databases. These are all examples:
  • Customer databases
  • Personal databases
  • Inventory databases

2.Analytical database

Analytical databases stores data and information extracted from selected operational and external databases. They consist of summarized data and information most needed by an organizations manager and other end user. They may also be called Management database or Information database.

3.Data warehouse

A data warehouse stores data from current and previous years that has been extracted from the various operational databases of an organization. It is the central source of data that has been screened, edited, standardized and integrated so that it can be used by managers and other end user professionals throughout an organization.

4.Distributed database

Distributed databases are databases of local work groups and departments at regional offices, branch offices, manufacturing plants and other work sites. These databases can include segments of both common operational and common user databases, as well as data generated and used only at a user’s own site.

5.End-user database

End-user databases consist of a variety of data files developed by end-users at their workstations. Examples of these are collection of documents in spreadsheets, word processing and even downloaded files.

6.External database

External databases where access to external, privately owned online databases or data banks is available for a fee to end users and organizations from commercial services. Access to a wealth of information from external database is available for a fee from commercial online services and with or without charge from many sources in the internet.

7.Hypermedia databases

Hypermedia databases are set of interconnected multimedia pages at a web-site. It consists of home page and other hyperlinked pages of multimedia or mixed media such as text, graphic, photographic images, video clips, audio etc.

8.Navigational database

Navigational databases are characterized by the fact that objects in it are found primarily by following references from other objects. Traditionally navigational interfaces are procedural, though one could characterize some modern systems like XPath as being simultaneously navigational and declarative.

9.In-memory databases

In-memory databases are database management systems that primarily rely on main memory for computer data storage. Main memory databases are faster than disk-optimized databases since the internal optimization algorithms are simpler and execute fewer CPU instructions. Accessing data in memory provides faster and more predictable performance than disk. In applications where response time is critical, such as telecommunications network equipment that operates 9-1-1 emergency systems, main memory databases are often used.

10.Document-oriented databases

Document-oriented databases are computer programs designed for document-oriented applications. These systems may be implemented as a layer above a relational database or an object database. As opposed to relational databases, document-based databases do not store data in tables with uniform sized fields for each record. Instead, each record is stored as a document that has certain characteristics. Any number of fields of any length can be added to a document. Fields can also contain multiple pieces of data.

11.Real-time databases

A real-time database is a processing system designed to handle workloads whose state is constantly changing. This differs from traditional databases containing persistent data, mostly unaffected by time. For example, a stock market changes very rapidly and is dynamic. Real-time processing means that a transaction is processed fast enough for the result to come back and be acted on right away. Real-time databases are useful for accounting, banking, law, medical records, multi-media, process control, reservation systems, and scientific data analysis. As computers increase in power and can store more data, they are integrating themselves into our society and are employed in many applications.
Database Management System:
A database management system (DBMS) is software that organizes the storage of data. It controls the creation, maintenance, and use of the database storage structures of an organization and its end users. It allows organizations to place control of organization wide database development in the hands of Database Administrators (DBAs) and other specialist. In large systems, a DBMS allows users and other software to store and retrieve data in a structured way.

Primary tasks of DBMS:

  • Database Development: It is used to define and organize the content, relationships, and structure of the data needed to build a database.
  • Database Interrogation: It can access the data in a database for information retrieval and report generation. End users can selectively retrieve and display information and produce printed reports and documents.
  • Database Maintenance: It is used to add, delete, update, correct, and protect the data in a database.
  • Application Development: It is used to develop prototypes of data entry screens, queries, forms, reports, tables, and labels for a prototyped application. Or use 4GL or 4th Generation Language or application generator to develop program codes.


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This article is the topic of 7th unit from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

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1 comment:

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