Databases

What is a Database?

A database is a persistent, organised store of related data.

Persistent
Organised
Related
Computerised Databases are better than Manual Databases (paper) because…

A computerised database is a collection of related data stored in one or more computerised files in a manner that can be accessed by users or computer programs. Most computerised databases are operational databases, meaning that data going into the database is used in real time to support the on-going activities of a business. A supermarket accounting system is an example: as items are sold, the inventory database is updated and the inventory information is made available to the sales staff. Computers have the ability to store large amounts of data in a compact space and to process it speedily. Organisations of all sizes use databases to store, sort, interrogate and manage their data.

Hospitals
Businesses
Internet Search engines
Database Levels

A database can be viewed at three levels:

Further details can be found here: Three levels acrhitecture DBS

External View:

This is what the user sees. It is a view that is designed to be useful for a particular job. Generally there will be a user-friendly interface that will allow the end-user to interact with the data contained within the database. The user does not need to be aware of the physical structure of the database, or how the data is stored within it. .

Conceptual View:

This is concerned with how the data is organised. It has to do with the design of the tables, the types of data stored, validation rules used and how tables are linked. This is the equivalent of the ‘Design View’ when using MS Access.


Physical View: