Revision

Revision

Chapter 1

Database Management System – This is a software package which, is used to create, manipulate and present data from electronic databases.

Database – this is a collection of related information about a ser of persons.

Traditional databases –

The storage of paper records was very bulky. Often requiring several large storing cabinets.
Data was often duplicated in several records.
Keeping records up-to-date was difficult and time consuming, and often resulted in data inconsistency, where duplicated values were updated in one record but not in others.

Benefits of using databases –

Searching and sorting operations can be performed much more quickly and easily.
Information is more easily available to users, due to improved methods of data retrieval.
Security and integrity of data is improved, due to the methods of data storage and updating.
No data redundancy (data duplication). In a relational database, data is never stored more often than is necessary.

Chapter 2

Relational model – the main idea behind a relational database is that data is grouped into entities that are related, in order to minimise data duplication and achieve data integrity.

In order to create a relational database, it is necessary first to produce a data model to represent the data being stored. The data model will indicate which entities are required, which attributes belong to each entity, and what relationships exist between the entities.