Introduction to Databases: Evolution, Types and Features

A database is an organized collection of structured information, or data, typically stored electronically in a computer system. A database is usually controlled by a database management system (DBMS). Together, the data and the DBMS, along with the applications that are associated with them, are referred to as a database system, often shortened to just database. [ [ ...]

Database Systems: Basic Definitions and Concepts

In an organization, the data is the most basic resource. To run the organization efficiently, the proper organization and management of data is essential. The formal definition of the major terms  used  in  databases  and  database systems  is  defined  in  this  section. 1. Data The term data may be defined as known facts that could [ [ ...]

Traditional File System Versus Database Systems

Conventionally, the data were stored and processed using traditional file processing systems. In these traditional file systems, each file is independent of other file, and data in different files can be integrated only by writing individual program for each application. The data and the application programs that uses the data are so arranged that any [ [ ...]

Database Systems: DBMS Users

The users of a database system can be classified into various categories depending upon their interaction  and  degree  of  expertise  of  the  DBMS. 1. End Users or Naive Users The end users or naive users use the database system through a menu-oriented application program, where the type and range of response is always displayed on [ [ ...]

Database or DBMS Languages

The DBMS provides different languages and interfaces for each category of users to express database queries and updations. When the design of the database is complete and the DBMS is chosen to implement it, the first thing to be done is to specify the conceptual and internal schemas for the database and the corresponding mappings. [ [ ...]

Database Systems: Schemas, Subschema and Instances

The plans of the database and data stored in the database are most important for an organization, since database is designed to provide information to the organization. The data stored in the database changes regularly but the plans remain static for longer periods of time. 1. Schema A schema is plan of the database that [ [ ...]

Three Level Architecture of Database Systems (DBMS)

The architecture is a framework for describing database concepts and specifying the structure of database system. The three level architecture was suggested by ANSI/SPARC. Here database is divided into three levels external level, conceptual level and internal level as shown in  Figure  1.7. 1. Levels or Views The three levels or views are discussed below: [ [ ...]

Database Systems: Data Models

A data model is a collection of concepts that can be used to describe the structure of the database including  data  types, relationships  and  the  constraints that  apply  on the  data. A data model helps in understanding the meaning of the data and ensures that, we understand. The data requirements of each The use of [ [ ...]

Types of Database Systems

The database systems can be  classified into three categories i.e., According to the number of users According to the type of use According to database site locations The various  types of  database systems  are as  follows: 1. According to the Number of Users According to the number of users, the database systems can be further [ [ ...]

Comparison between Client/Server and Distributed Database System

Source: Gupta Satinder Bal, Mittal Aditya (2017), Introduction to Database Management System, 2nd Edition-University Science Press [ ...]

E-R and EER Models: Basic Concepts

1. Enterprise Enterprise refers to any kind of organization. Ex. Colleges, schools, banks, any company etc. 2. Entity Entity refers to an “object” or “thing” in real world. Object may be any person, place, event etc. Ex. Students of colleges and schools, loans in banks, employees in any company etc. 3. Attributes These are the [ [ ...]

E-R and EER Models: Types of Attributes

Attributes can be characterized by the following Three major types : 1. Simple and Composite Attributes Simple Attributes  are those  which cannot  be  divided into  subparts. Ex. Age of student         Composite Attributes  are those  which can  be  divided into  subparts. Ex. Name of a student can be divided into First Name, Middle Name, and Last [ [ ...]

E-R and EER Models: Relationship Sets

Relationship : A relationship is the association among several It connects different entities through a  meaningful relation. Relationship Set : A relationship set  is  a set  of relationships  of the  same type. Consider an example, employees work in different departments. Then relationship exists between employees and departments because each employee must belongs to some department. [ [ ...]

E-R and EER Models: Mapping Constraints

There are certain constraints in E-R model. Data in the database must follow the constraints. Constraints act as rules to which the contents of database must conform. There are two types of mapping constraints : (a) Mapping cardinalities, (b) Participation constraints. 1. Mapping Cardinalities (Cardinality Ratios) It specifies the number of entities of an entity [ [ ...]

E-R and EER Models: Keys

A key is an attribute or set of attributes that is used to identify data in entity sets. The attributes which are used as key are known as key attributes. Rest of all are known as Non-key attributes. 1. Types of Keys There are many keys that are used in the different tables. These are [ [ ...]

E-R and EER Models: Entity – Relationship Diagram

E-R diagrams represents the logical structure of a database. Symbols used in E-R diagrams are shown  in Table 2.1. Examples : Make an E-R diagram having two entity sets, Customer and Item. Cardinality Ratio is many to many because a customer can buy any number of items and same item can  be purchased by more  [ [ ...]

E-R and EER Models: Types of Entity Sets

There are two types of entity  sets as given below: 1. Strong Entity Sets Entity set having any  key attributes are known as Strong Entity  sets. Ex. The Figure  2.12 shows strong  entity set Student  having key attribute  Reg_No. 2. Weak Entity Sets Entity sets having no key attributes are known as Weak Entity sets. [ [ ...]

Enhanced Entity-Relationship (EER) Model

EER model is basically the enhanced version of E-R model which includes all the basic concepts of E-R model with capability to support additional semantic concepts of complex applications. These  additional  concepts  are  : Specialization Generalization Categorization. Before discussing the concepts of specialization, generalization, and categorization two another entity  types  superclass  (supertype) and  subclass  (subtype)  [ [ ...]

Reduction of an E-R and EER Diagram into Tables

To represent the database in tabular form, E-R diagrams have to be reduced in tables. For each entity set, make different table and for each relationship set make a different table. 1. Reduction of Strong Entity Sets into Tables For a strong entity set E with attributes a1, a2, …, an, make a table having [ [ ...]

File Organization: Basic Concepts of Files

A file is a collection of related sequence of records. A collection of field names and their corresponding data types constitutes a record. A data type, associated with each field, specifies the types of values a field can take. All records in a file are of the same record type. 1. Records and Record Types [ [ ...]