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Introduction
to Database
Data may be
logical organized into characters, fields, records, files, and database, just
as writing can be organized in letters, sentences, words, paragraph, and
documents. Example of logical data elements are given below
Character:
The most basic data element is the character,
which consists of a single alphabetic or numeric or any other symbol. The bit
or byte is more elementary data element but those terms refer to the physical
storage elements provided by the computer hardware. From a user’s point of view
, a character is the most basic element that may be observed and manipulated.
Field:
The next
higher level of data is the data item or field. A field consists of a group of characters.
For example, the group of alphabetic characters in a person’s name forms’ a name
field.A data field represents an attribute of some entity. For example an
employee’s salary is an attribute that is a typical data fiel
d used to describe
an entity that is an employee.
Record:
Related field of
data are grouped to form a record. A record represents a collection of
attributes that describes an entity. An example is the payroll for a person,
which consists of data fields describing attributes such as the person’s name
and social security and rate of payment.
Fixed length records contain in a fixed number of fixed length data fields.
Variable-length records contain a variable number of fields and field lengths.
Field:
A group of
related records forms a data file or table. Thus an employee file contains the records of the
employees of a firm. Fields are frequently classified by the application for
which they are primarily used, such as a payroll file or an inventory file.or
the type which they are contain.
Database:
A data base is an integrated collection of
logically related records or objects. An object consists of data values
describing the attributes of an entity, plus the operations that can be
performed upon the data. A database consolidates records previously stored
in separate files into a common pool of
data records that provides data for many application. The data stored in a
database are independent of the application programs using them and of the type
of secondary storage devices on which they are stored.
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