PLANNING A DATABASE (Database Design Steps / Planning Database) :-
Database planning is a systematic approach to the development of database that moves from concept to design and development to implementation. A well-designed database promotes Consistent data entry and retrieval. Database should be planned in a systematic way to save time, efforts and make it perform the expected tasks. The time and Work required to plan a database depends on its complexity.
The following steps are involved in planning a database.
In this step the nature and scope of the problem, to be solved, is identified and the problem is clearly defined. The database developers must know what type of information is given and what are the unknowns. They have to analyse the problem to gather as much information as possible for finding a solution. For example, the Examination Section Head of a College has been getting complaints of poor Examination services from the Examination department. This may lead an initial investigation to find whether a new system can solve the problem. If the report suggests a new system, this leads to the next phase which is the feasibility study of the new system.
Feasibility Study The purpose of feasibility study is to find one or more solutions of the problem and to suggest the most desirable and economical solution. For this purpose the database developer needs to generate several solutions of the problem to accomplish the desired task and propose one solution. Feasibility study includes the following.
• Investigate the problem
• Find out all the possible solutions available
• Study all the solutions to determine their feasibility
• List the issues with each solution
• Select the preferred solution for implementation
• Document the results in a feasibility report
The purpose of requirement analysis is to obtain thorough and detailed understanding of the problem. It is important to create a complete and accurate representation of all the requirements. Only then, it is possible to develop a database that fully satisfies the requirements.
For example, to develop ‘College Examination System’ a detailed study is needed to analyse the requirements. This will include the following:
– Entities required i.e. the number of tables (database files) required (like Student, Exam, Exam Type, Result, Courses, etc.)
– Fields required for each entity in each table (like Roll No., Name, Class, Section, etc. for Student entity)
– Key field in each table
– Data types to fields
– Relationship between entities
– Forms design
identify Entities and Attributes After requirements identification, the next step is to identify the entities and its attributes. An entity is the main data object that is of significant interest to the organization. It is usually a person, place, thing, or event to be recorded in the database. An Attribute is a property that describes an entity. For example if employee is an entity then, the employee’s name, age, address, salary and job etc. are the attributes
For example, to develop ‘College Examination System’ the following entities and attributes will be required.
Assigning Names to Tables and Columns
Once entities and attributes are identified, entities are converted to tables and attributes to Columns of the tables. There are no standard conventions for naming tables and Columns but all names should be meaningful and consistent throughout the database. For example “Student” for Student’s table. In Case of attributes, meaningful names should be used wherever possible.
For example, the College Exam System may have the table name ‘Student and the Columns (attributes) may be assigned the names, Roll number, Name, Class, Section, Date of birth, Address.