CSC 422 L ECTURE N OTE DataBase Design by Aborisade D.O. Department of Computer Science, College of Natural Science, Federal University of Agriculture, Abeokuta (FUNAAB)

C OURSE C ONTENTS Meaning of Database Examples of Database Relational Database Design Conceptual Database Design Logical Database Design References

W HAT IS A D ATABASE ? A database is a collection of entities and its relation stored in a persistent and systematic way. Any database definition must include ENTITY, RELATION, PERSISTENT and SYSTEMATIC. Database is a collection of objects and relationships. A database is usually represented by drawing a cylindrical object because it (database) must reside in a device e.g an Utility and Hospital database are illustrated below:

D IAGRAM OF U TILITY D ATABASE Entities: Customer, bills, meters, payments, meter readings Relationships: bills sent to customers, Customers make payments, Customers use meters. Billing Meter reading Payment processin g Service start/stop

D IAGRAM OF H OSPITAL D ATABASE treatment symptons monitoring Diagnosis service start/stop Entities: patients, providers, treatments, diagnosis, symptons. Relationship: patients have symptons, provider prescibes treatments, provider make diagnosis

R ELATIONAL D ATABASE D ESIGN It is very likely that when Database application is developed and is being used, a user do more than just access the information. It is common to find out that an application developer is involved in the design of a database. Even if a developer is not responsible for constructing the database, knowing what makes a good database design can help come up with better strategies for accessing that data. So, an understanding of database design is important to a professional database designer and developer.

D ATABASE D ESIGN CONTD. A well design database structure for database makes a lot of difference between creating a successful database application and the one that is not successful. A poor design would cause problems of performance, integrity, and functionality limitations, which the best code can not do anything about. A database is said to be of good design when it is efficient, flexible, and fast enough to handle many users.

D ATABASE D ESIGN Database could be designed either by * Use of wizards tools or *Designing following the basic rules and guidelines. The starting points for an effective database are always the same: Understand what are the goals for the business in developing the application Determine what information and processes are needed to meet these goals. These lead to what we call The Conceptual Design.

C ONCEPTUAL AND L OGICAL D ESIGN There are two levels of database design namely: Conceptual design and Logical Database Design For example : Considering designing a database application for a Music Store. The owner of the store has several music stores and is planning to expand still further to a level where he/she wants to keep accurate records of all inventory in the various stores. In broad term, we could identity the following goals that our database design must enable and facilitate in this scenario:

E NTITIES, A TTRIBUTES, AND V ALUES Save information regarding all recordings stocked by his/her stores, with a mechanism fro flexibility searching this data, say by song, title, artist, or album name. Keep accurate track of inventories in any store. Store information about customer orders so that she can accurately track the progress of these orders. Store information about customers so that she/he can inform them when an order is available. The highlighted words above reflect most significant

E NTITIES, A TTRIBUTE, AND V ALUES pieces of information required for the business. And are referred to as the entities in the system. An entity represents some object in reality, such as a person, or thing. Entities, as objects represent a class of things. For example, in a customer entity, then Each instance of that object will represent a specific Customer. Each instance of the entity customer will have identical attributes that define the meaning of that entity e.g

E NTITIES, A TTRIBUTES, V ALUES Customer First Name Customer Last Name Postal Address Address Phone Number Each of these attributes will store values, and these values would be different from one customer instance to another.

C ONCEPTUAL D ESIGN The goal of the above exercise is to come up with a meaningful representation of the system, with various entities identified and an understanding of what services those portions will provide. It is worthy of note to observe that Conceptual design will not describe how things are done, but rather what needs to be done.

L OGICAL D ATABASE D ESIGN In Logical Database Design, we need not to concentrate on what needs to be done, but how things are done in a system. Logical design will be a very detailed specification of all entities. A logical design has to include more than just what was considered in the conceptual design. It has to include interaction between entities. Part of logical design efforts is to determine some of the entities that are required; how these entities would coexist and interact. This will lead us to drawing an ER diagram (Entity Relationship diagram).

R EFERENCES Kevin,M., Todd, Lauinger, John, C. etal.,: Beginning Java Databases.Wrox Press Limited Neil Mathew and Richard Stones: Beginning Databases with MySql. Wrox Press Limited. 2002