Introduction To DatabaseManagementSystem

A database consists of four elements as given

1. Data


2. Relationship


3. Schema


4. Constraints

Data

• Data are binary computer representations of stored logical entities.

• Software is divided into two general categories-data and programs

• A program is a collection of instruction for manipulating data

• Data exist is various forms- as numbers tents on pieces of paper,as bits and bytes stored in electronic memory or as facts stored in a persons mind

Relationship

• Relationships explain the correspondence between various data elements

Constraints

• Are predicates that define correct database states

Scheme

• Schema describes the organization of data and relationships within the database

• Schema defines various views of the database for the use of various system components of the database management system and for the application’s security

• A schema separates physical aspects of data storage form the logical aspects of data representation

• In database management systems data files are the files that store the database information whereas offer files, such as index files and data dictionaries, store administrative information known as metadata.

• Data base are organized by fields, records and files.
  

1. Fields: is a single piece of information.


2. Record: is one complete set of fields.


3. File: is a collection of records

Types of schema

1. Internal schema: defines how and where the data are
   organized in physical data storage.


2. Conceptual schema: defines the stored data structures in
   terms of the database model used.


3. External schema: defines a view (or) views of the database
   for particular uses