Design , implementation and management of secured lan

5.4.0.3 Database design

Database design is the process of producing a detailed data model of a database. It contains all the needed logical and physical design choices and physical storage parameters needed to generate a design in data definition language, which can then be used to create a database. It can also be used to describe many different parts of the design of an overall database system.

The process of doing database design generally consists of a number of steps which will be carried out by the database designer. Usually, the designer must:

· Determine the relationships between the different data elements.

· Superimpose a logical structure upon the data on the basis of these relationships.

5.4.0.3.0 Design process

The following are the steps to be followed during database design:

i). Determine the purpose of the database - This helps prepare for the remaining steps.

ii). Find and organize the information required - Gather all of the types of information to record in the database, such as product name and order number.

iii). Divide the information into tables - Divide information items into major entities or subjects, such as problem. Each subject then becomes a table.

iv). Turn information items into columns - Decide what information needs to be stored in each table. Each item becomes a field, and is displayed as a column in the table. For example, an Admin table might include fields such as user name and password.

v). Specify primary keys - Choose each table's primary key. The primary key is a column, or a set of columns, that is used to uniquely identify each row. An example might be user ID or Problem ID.

vi). Set up the table relationships - Look at each table and decide how the data in one table is related to the data in other tables. Add fields to tables or create new tables to clarify the relationships, as necessary.

vii). Refine the design - Analyze the design for errors. Create tables and add a few records of sample data. Check if results come from the tables as expected. Make adjustments to the design, as needed.

viii). Apply the normalization rules - Apply the data normalization rules to see if tables are structured correctly. Make adjustments to the tables

The person who is doing the design of a database is a person with expertise in the area of database design, rather than expertise in the domain from which the data to be stored is drawn e.g. financial information, biological information etc. Therefore the data to be stored in the database must be determined in cooperation with a person who does have expertise in that domain, and who is aware of what data must be stored within the system.

This process is one which is generally considered part of requirement analysis, and requires skill on the part of the database designer to elicit the needed information from those with the domain knowledge.