Mapping is a process of converting on level to another level. There are two levels of mapping: • From the conceptual level to the internal level • From the external level to the conceptual level [ad#ad-2] Conceptual / Internal Mapping:
February 21, 2010 | Database Management System | Comments Off
Mapping is a process of converting on level to another level. There are two levels of mapping:
• From the conceptual level to the internal level
• From the external level to the conceptual level
Conceptual / Internal Mapping:
The conceptual/internal mapping defines the association between the abstract view and stored database. It specifies how conceptual records [...]
February 21, 2010 | Database Management System | Comments Off
Database can he viewed at three levels. The levels form three-level architecture and are depicted by three models. The models refer to the permanent structure of the database, not to the data that is stored at any given moment. A database model is a collection of tools. It may include a type of diagram [...]
February 21, 2010 | Database Management System | Comments Off
Dr. E. F. Codd worked to improve the working of DBMSs for handling large volumes of data. He applied the rules of mathematics for solving the problems of earlier database models. Some important problems were:
• Data integrity
• Data redundancy
Dr. Codd presented a paper “A Relational Model of Data for Large Shared Databanks” in June [...]
February 21, 2010 | Database Management System | Comments Off
To overcome the problems of the hierarchical data model, the Network Model was developed. The network model modified the hierarchical model by allowing multiple parent-child relationships. These relationships are known as sets in a network model. The network model structures and language constructs were defined by the CODASYL (Conference on Data Systems Language).
1. Characteristics [...]
February 18, 2010 | Database Management System | Comments Off
One of the earliest database management systems was based on the hierarchical model. In a hierarchical data model, the records have a parent-child relationship.
Consider the application used for Production Planning in automobile manufacturing companies. The model of the database is shown in the following figure. The automobile manufacturer manufactures various models of cars. Each car [...]
February 18, 2010 | Database Management System | Comments Off
Another way to design an information system is known as staged database design approach. It is a top-down approach. It begins by analyzing the general requirements of the organization: As the process continues, these problems are analyzed in more details. The steps in this approach are as follows:
Analyze User Environment:
The first step in [...]
February 14, 2010 | Database Management System | Comments Off
System development life cycle (SDLC) is a conventional way for developing an. information system. It consists of many steps and involves different persons. Different step of SDLC are as follows:
Preliminary Investigation:
Preliminary investigation is the first phase of System Development Life Cycle. The main objective of this phase is to identify deficiencies and requirements [...]
February 14, 2010 | Database Management System | Comments Off
The development of a complete database application is a lengthy and complicated process. Different strategies can be used to develop database applications. Following is a brief discussion about different strategies and steps performed during this process:
General Strategies:
A database application is developed to satisfy the requirements of the user. It is very important to [...]
February 11, 2010 | Database Management System | Comments Off
There are different types of user that play different roles in a database environment. Following is a brief description of these users:
(1) Application Programmers:
Application programmer is the person who is responsible for implementing the required functionality of database for the end user. Application programmer works according to the specification provided by the system [...]
February 11, 2010 | Database Management System | Comments Off
The range of database application is as follows:
(1) Personal Computer Database:
Personal computer databases are specially designed for single user. The user may be using stand-alone desktop computer or laptop. The representatives of a medical company may use laptop computers when working in the market. This computer may use a simple database application in [...]