Database Design
To develop a database that satisfies that information needs
of today as well as of tomorrow, it is necessary to understand the database
conceptually. The first task of the designer is to develop the Conceptual Model.
The conceptual model is independent model independent of the user applications,
the hardware and the DBMS.
The steps in the development of the conceptual model are:
- Data
analysis
-
Relational Identity
-
Graphical representation
- Design
process
The database administrator should initiate a plan to collect
the data needs of each person in the organization. It is necessary to
investigate further as to how the data is processed by these persons in
executing their functional responsibilities.
Collect all the names of the data entities and determine its
description and spell out in brief the use of it the operations and the
management of organization. As
mentioned earlier, the entity is to be described by its attributes. An attribute should be described with the
details, viz.
Name and description
Source
Characteristics of attitude – Numeric, Alpha, its unit of
measure, its value range.
Use of the attribute in the various applications.
Security, Access, Read, update protocols.
Importance: Importance in the database.
Attribute relationships
The conceptual model is used to develop a logical model which
can be implemented with the relational, hierarchical or network model of the
Database Management System.
The major concept used form the relational theory is
Normalization. The normalization process groups the entities and attributes in
the form of two-way tables.
The major concept used from the relational theory is
Normalization. The normalization process groups the entities and attributes in
the form of two-way tables.
The first step in the normalization process consists of
transforming the entities into two dimensional tables. There are five forms of normalization. The fourth and the fifth forms are
difficult to achieve and handle.
The form of the data is called as the Un-normalised because
at the crossing of the row and the column, more than one value of an attribute
is present. For example, for one patient identified by a unique primary key the
`Patient Number', there are two values of the surgeon registration number, and
two types of surgery. Hence, for a
given patient, we cannot determine the value of the non-key attribute uniquely.
When the data is in such form it is called as an un-normalised. The normalization process in stages
brings data uniquely into the Normal Form.
First Normal Form: A relation in the first normal form is a
table. At every intersection of the row and the column there can be only one
value. No groups of values are
permitted at the intersection.
It is necessary to examine systematically the purpose of the
input data which will find place in the database of the desired outputs. The design process considers information
requirements of many different types of users (data views) and designs the
inputs for the database. The
conceptual relationships will decide the key data entities and its attributes.
While designing the database, these elements play an important role.
