Wednesday, January 30, 2013

DBMS


A database is a collection of occurrence of multiple record types containing the relationship between records, data aggregate and data items. A database may be defined as
      A database is a collection of interrelated data store together without harmful and unnecessary redundancy (duplicate data) to serve multiple applications
      The data is stored so that they are independent of programs, which use the data. A common and control approach is used in adding the new data, modifying and retrieving existing data or deletion of data within the database A running database has function in a corporation, factory, government department and other organization. Database is used for searching the data to answer some queries. A database may be design for batch processing, real time processing or on line processing.

DATABASE SYSTEM
      Database System is an integrated collection of related files along with the detail about their definition, interpretation, manipulation and maintenance. It is a system, which satisfied the data need for various applications in an organization without unnecessary redundancy. A database system is based on the data. Also a database system can be run or executed by using software called DBMS (Database Management System). A database system controls the data from unauthorized access.

Foundation Data Concept:
A hierarchy of several levels of data has been devised that differentiates between different groupings, or elements, of data. Data are logically organized into:

Character
      It is the most basic logical data element. It consists of a single alphabetic, numeric, or other symbol.

Field
      It consists of a grouping of characters. A data field represents an attribute (a characteristic or quality) of some entity (object, person, place, or event).

Record
      The related fields of data are grouped to form a record. Thus, a record represents a collection of attributes that describe an entity. Fixed-length records contain, a fixed number of fixed-length data fields. Variable-length records contain a variable number of fields and field lengths.

File
      A group of related records is known as a data file, or table. Files are frequently classified by the application for which they ar primarily used, such as a payroll file or an inventory file, or the type of data they contain, such as a document file or a graphical image file. Files are also classified by their permanence, for example, a master file versus a transaction file. A transaction file would contain records of all transactions occurring during a period, whereas a master file contains all the permanent records. A history file is an obsolete transaction or master file retained for backup purposes or for long-term historical storage called archival storage.

Database

      It is an integrated collection of logically related records or objects. A database consolidates records previously stored in separate files into a common pool of data records that provides data for many applications. The data stored in a database is independent of the application programs using it and o the ‘type of secondary storage devices on which it is stored.

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